Cisco Systems Ios Xr Users Manual

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Cisco IOS XR Routing Configuration Guide
Contents
Preface

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Cisco IOS XR Routing Configuration Guide

Cisco IOS XR Software Release 3.2

Text Part Number: OL-5554-05

THE SPECIFICATIONS AND INFORMATION REGARDING THE PRODUCTS IN THIS MANUAL ARE SUBJECT TO CHANGE WITHOUT NOTICE. ALL

STATEMENTS, INFORMATION, AND RECOMMENDATIONS IN THIS MANUAL ARE BELIEVED TO BE ACCURATE BUT ARE PRESENTED WITHOUT

WARRANTY OF ANY KIND, EXPRESS OR IMPLIED. USERS MUST TAKE FULL RESPONSIBILITY FOR THEIR APPLICATION OF ANY PRODUCTS.

THE SOFTWARE LICENSE AND LIMITED WARRANTY FOR THE ACCOMPANYING PRODUCT ARE SET FORTH IN THE INFORMATION PACKET THAT

SHIPPED WITH THE PRODUCT AND ARE INCORPORATED HEREIN BY THIS REFERENCE. IF YOU ARE UNABLE TO LOCATE THE SOFTWARE LICENSE

OR LIMITED WARRANTY, CONTACT YOUR CISCO REPRESENTATIVE FOR A COPY.

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WITHOUT LIMITATION, LOST PROFITS OR LOSS OR DAMAGE TO DATA ARISING OUT OF THE USE OR INABILITY TO USE THIS MANUAL, EVEN IF CISCO

OR ITS SUPPLIERS HAVE BEEN ADVISED OF THE POSSIBILITY OF SUCH DAMAGES.

Cisco IOS XR Routing Configuration Guide

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All other trademarks mentioned in this document or Website are the property of their respective owners. The use of the word partner does not imply a partnership relationship

between Cisco and any other company. (0502R)

RC-iii

Cisco IOS XR Routing Configuration Guide

CONTENTS

Preface xi

Document Revision History xi

Obtaining Documentation xii

Cisco.com xii

Product Documentation DVD xii

Ordering Documentation xii

Documentation Feedback xiii

Cisco Product Security Overview xiii

Reporting Security Problems in Cisco Products xiii

Obtaining Technical Assistance xiv

Cisco Technical Support & Documentation Website xiv

Submitting a Service Request xv

Definitions of Service Request Severity xv

Obtaining Additional Publications and Information xv

Implementing BGP on Cisco IOS XR Software RC-1

Contents RC-1

Prerequisites for Implementing BGP on Cisco IOS XR Software RC-2

Information About Implementing BGP on Cisco IOS XR Software RC-2

BGP Functional Overview RC-2

BGP Router Identifier RC-3

BGP Default Limits RC-3

BGP Validation of Local Next-Hop Addresses RC-4

BGP Configuration RC-4

No Default Address Family RC-15

Routing Policy Enforcement RC-16

Table Policy RC-18

Update Groups RC-18

BGP Best Path Algorithm RC-18

Multiprotocol BGP RC-21

Route Dampening RC-23

BGP Routing Domain Confederation RC-24

BGP Route Reflectors RC-24

Default Address Family for show Commands RC-27

Contents

RC-iv

Cisco IOS XR Routing Configuration Guide

How to Implement BGP on Cisco IOS XR Software RC-27

Enabling BGP Routing RC-28

Configuring a Routing Domain Confederation for BGP RC-31

Resetting eBGP Session Immediately Upon Link Failure RC-33

Logging Neighbor Changes RC-34

Adjusting BGP Timers RC-34

Changing the BGP Default Local Preference Value RC-35

Configuring the MED Metric for BGP RC-36

Configuring BGP Weights RC-38

Tuning the BGP Best Path Calculation RC-39

Indicating BGP Backdoor Routes RC-41

Configuring Aggregate Addresses RC-43

Redistributing iBGP Routes into IGP RC-44

Redistributing Prefixes into Multiprotocol BGP RC-46

Configuring BGP Route Dampening RC-48

Applying Policy When Updating the Routing Table RC-52

Setting BGP Administrative Distance RC-53

Configuring a BGP Neighbor Group RC-55

Configuring a BGP Neighbor RC-58

Configuring a Route Reflector for BGP RC-60

Configuring BGP Route Filtering by Route Policy RC-62

Disabling Next Hop Processing on BGP Updates RC-64

Configuring BGP Community and Extended-Community Filtering RC-65

Configuring Software to Store Updates from a Neighbor RC-67

Disabling a BGP Neighbor RC-69

Resetting Neighbors Using BGP Dynamic Inbound Soft Reset RC-71

Resetting Neighbors Using BGP Outbound Soft Reset RC-71

Resetting Neighbors Using BGP Hard Reset RC-72

Clearing Caches, Tables and Databases RC-73

Displaying System and Network Statistics RC-73

Monitoring BGP Update Groups RC-75

Configuration Examples for Implementing BGP on Cisco IOS XR Software RC-76

Enabling BGP: Example RC-76

Displaying BGP Update Groups: Example RC-77

BGP Neighbor Configuration: Example RC-78

BGP Confederation: Example RC-78

BGP Route Reflector: Example RC-79

Where to Go Next RC-79

Additional References RC-80

Contents

RC-v

Cisco IOS XR Routing Configuration Guide

Related Documents RC-256

Standards RC-256

MIBs RC-256

RFCs RC-256

Technical Assistance RC-256

Contents

RC-x

Cisco IOS XR Routing Configuration Guide

Preface

This is the preface for the Cisco IOS XR Routing Configuration Guide.

The preface contains the following sections:

•Document Revision History, page xi

•Obtaining Documentation, page xii

•Documentation Feedback, page xiii

•Cisco Product Security Overview, page xiii

•Obtaining Technical Assistance, page xiv

•Obtaining Additional Publications and Information, page xv

Document Revision History

The Document Revision History table records technical changes to this document. Table 1 shows the

document revision number for the change, the date of the change, and a brief summary of the change.

Note that not all Cisco documents use a Document Revision History table.

Table 1 Document Revision History

Revision Date Change Summary

OL-5554-05 November

2005

Added description for the OSPFv3 Graceful Restart feature.

Added descriptions for the multicast-intact option in IS-IS and OSPFv2.

OL-5554-04 August 31,

2005

Implementing IS-IS on Cisco IOS XR Software changes:

Updated the IS-IS module to include the ability to configure a broadcast

medium connecting two networking devices as a point-to-point link.

OL-5554-02 October 31,

2004

Implementing IS-IS on Cisco IOS XR Software changes:

Changes to lsp-gen-interval, spf-interval, and show isis spf-log information.

OL-5554-01 July 30, 2004 Initial release of this document.

Preface

Obtaining Documentation

xii

Cisco IOS XR Routing Configuration Guide

Obtaining Documentation

Cisco documentation and additional literature are available on Cisco.com. Cisco also provides several

ways to obtain technical assistance and other technical resources. These sections explain how to obtain

technical information from Cisco Systems.

Cisco.com

You can access the most current Cisco documentation at this URL:

http://www.cisco.com/techsupport

You can access the Cisco website at this URL:

http://www.cisco.com

You can access international Cisco websites at this URL:

http://www.cisco.com/public/countries_languages.shtml

Product Documentation DVD

Cisco documentation and additional literature are available in the Product Documentation DVD package,

which may have shipped with your product. The Product Documentation DVD is updated regularly and

may be more current than printed documentation.

The Product Documentation DVD is a comprehensive library of technical product documentation on

portable media. The DVD enables you to access multiple versions of hardware and software installation,

configuration, and command guides for Cisco products and to view technical documentation in HTML.

With the DVD, you have access to the same documentation that is found on the Cisco website without

being connected to the Internet. Certain products also have .pdf versions of the documentation available.

The Product Documentation DVD is available as a single unit or as a subscription. Registered Cisco.com

users (Cisco direct customers) can order a Product Documentation DVD (product number

DOC-DOCDVD=) from Cisco Marketplace at this URL:

http://www.cisco.com/go/marketplace/

Ordering Documentation

Beginning June 30, 2005, registered Cisco.com users may order Cisco documentation at the Product

Documentation Store in the Cisco Marketplace at this URL:

http://www.cisco.com/go/marketplace/

Nonregistered Cisco.com users can order technical documentation from 8:00 a.m. to 5:00 p.m.

(0800 to 1700) PDT by calling 1 866 463-3487 in the United States and Canada, or elsewhere by

calling 011 408 519-5055. You can also order documentation by e-mail at

tech-doc-store-mkpl@external.cisco.com or by fax at 1 408 519-5001 in the United States and Canada,

or elsewhere at 011 408 519-5001.

Preface

Documentation Feedback

xiii

Cisco IOS XR Routing Configuration Guide

Documentation Feedback

You can rate and provide feedback about Cisco technical documents by completing the online feedback

form that appears with the technical documents on Cisco.com.

You can send comments about Cisco documentation to bug-doc@cisco.com.

You can submit comments by using the response card (if present) behind the front cover of your

document or by writing to the following address:

Cisco Systems

Attn: Customer Document Ordering

170 West Tasman Drive

San Jose, CA 95134-9883

We appreciate your comments.

Cisco Product Security Overview

Cisco provides a free online Security Vulnerability Policy portal at this URL:

http://www.cisco.com/en/US/products/products_security_vulnerability_policy.html

From this site, you can perform these tasks:

•Report security vulnerabilities in Cisco products.

•Obtain assistance with security incidents that involve Cisco products.

•Register to receive security information from Cisco.

A current list of security advisories and notices for Cisco products is available at this URL:

http://www.cisco.com/go/psirt

If you prefer to see advisories and notices as they are updated in real time, you can access a Product

Security Incident Response Team Really Simple Syndication (PSIRT RSS) feed from this URL:

http://www.cisco.com/en/US/products/products_psirt_rss_feed.html

Reporting Security Problems in Cisco Products

Cisco is committed to delivering secure products. We test our products internally before we release them,

and we strive to correct all vulnerabilities quickly. If you think that you might have identified a

vulnerability in a Cisco product, contact PSIRT:

•Emergencies— security-alert@cisco.com

An emergency is either a condition in which a system is under active attack or a condition for which

a severe and urgent security vulnerability should be reported. All other conditions are considered

nonemergencies.

•Nonemergencies—psirt@cisco.com

In an emergency, you can also reach PSIRT by telephone:

•1 877 228-7302

•1 408 525-6532

Preface

Obtaining Technical Assistance

xiv

Cisco IOS XR Routing Configuration Guide

Tip We encourage you to use Pretty Good Privacy (PGP) or a compatible product to encrypt any sensitive

information that you send to Cisco. PSIRT can work from encrypted information that is compatible with

PGP versions 2.x through 8.x.

Never use a revoked or an expired encryption key. The correct public key to use in your correspondence

with PSIRT is the one linked in the Contact Summary section of the Security Vulnerability Policy page

at this URL:

http://www.cisco.com/en/US/products/products_security_vulnerability_policy.html

The link on this page has the current PGP key ID in use.

Obtaining Technical Assistance

Cisco Technical Support provides 24-hour-a-day award-winning technical assistance. The Cisco

Technical Support & Documentation website on Cisco.com features extensive online support resources.

In addition, if you have a valid Cisco service contract, Cisco Technical Assistance Center (TAC)

engineers provide telephone support. If you do not have a valid Cisco service contract, contact your

reseller.

Cisco Technical Support & Documentation Website

The Cisco Technical Support & Documentation website provides online documents and tools for

troubleshooting and resolving technical issues with Cisco products and technologies. The website is

available 24 hours a day, at this URL:

http://www.cisco.com/techsupport

Access to all tools on the Cisco Technical Support & Documentation website requires a Cisco.com user

ID and password. If you have a valid service contract but do not have a user ID or password, you can

http://tools.cisco.com/RPF/register/register.do

Note Use the Cisco Product Identification (CPI) tool to locate your product serial number before submitting

a web or phone request for service. You can access the CPI tool from the Cisco Technical Support &

Documentation website by clicking the Tools & Resources link under Documentation & Tools. Choose

Cisco Product Identification Tool from the Alphabetical Index drop-down list, or click the Cisco

Product Identification Tool link under Alerts & RMAs. The CPI tool offers three search options: by

product ID or model name; by tree view; or for certain products, by copying and pasting show command

output. Search results show an illustration of your product with the serial number label location

highlighted. Locate the serial number label on your product and record the information before placing a

service call.

Preface

Obtaining Additional Publications and Information

Cisco IOS XR Routing Configuration Guide

Submitting a Service Request

Using the online TAC Service Request Tool is the fastest way to open S3 and S4 service requests. (S3

and S4 service requests are those in which your network is minimally impaired or for which you require

product information.) After you describe your situation, the TAC Service Request Tool provides

recommended solutions. If your issue is not resolved using the recommended resources, your service

request is assigned to a Cisco engineer. The TAC Service Request Tool is located at this URL:

http://www.cisco.com/techsupport/servicerequest

For S1 or S2 service requests or if you do not have Internet access, contact the Cisco TAC by telephone.

(S1 or S2 service requests are those in which your production network is down or severely degraded.)

Cisco engineers are assigned immediately to S1 and S2 service requests to help keep your business

operations running smoothly.

To open a service request by telephone, use one of the following numbers:

Asia-Pacific: +61 2 8446 7411 (Australia: 1 800 805 227)

EMEA: +32 2 704 55 55

USA: 1 800 553-2447

For a complete list of Cisco TAC contacts, go to this URL:

http://www.cisco.com/techsupport/contacts

Definitions of Service Request Severity

To ensure that all service requests are reported in a standard format, Cisco has established severity

definitions.

Severity 1 (S1)—Your network is “down,” or there is a critical impact to your business operations. You

and Cisco will commit all necessary resources around the clock to resolve the situation.

Severity 2 (S2)—Operation of an existing network is severely degraded, or significant aspects of your

business operation are negatively affected by inadequate performance of Cisco products. You and Cisco

will commit full-time resources during normal business hours to resolve the situation.

Severity 3 (S3)—Operational performance of your network is impaired, but most business operations

remain functional. You and Cisco will commit resources during normal business hours to restore service

to satisfactory levels.

Severity 4 (S4)—You require information or assistance with Cisco product capabilities, installation, or

configuration. There is little or no effect on your business operations.

Obtaining Additional Publications and Information

Information about Cisco products, technologies, and network solutions is available from various online

and printed sources.

•Cisco Marketplace provides a variety of Cisco books, reference guides, documentation, and logo

merchandise. Visit Cisco Marketplace, the company store, at this URL:

http://www.cisco.com/go/marketplace/

Preface

Obtaining Additional Publications and Information

xvi

Cisco IOS XR Routing Configuration Guide

•Cisco Press publishes a wide range of general networking, training and certification titles. Both new

and experienced users will benefit from these publications. For current Cisco Press titles and other

information, go to Cisco Press at this URL:

http://www.ciscopress.com

•Packet magazine is the Cisco Systems technical user magazine for maximizing Internet and

networking investments. Each quarter, Packet delivers coverage of the latest industry trends,

technology breakthroughs, and Cisco products and solutions, as well as network deployment and

troubleshooting tips, configuration examples, customer case studies, certification and training

information, and links to scores of in-depth online resources. You can access Packet magazine at

this URL:

http://www.cisco.com/packet

•iQ Magazine is the quarterly publication from Cisco Systems designed to help growing companies

learn how they can use technology to increase revenue, streamline their business, and expand

services. The publication identifies the challenges facing these companies and the technologies to

help solve them, using real-world case studies and business strategies to help readers make sound

technology investment decisions. You can access iQ Magazine at this URL:

http://www.cisco.com/go/iqmagazine

or view the digital edition at this URL:

http://ciscoiq.texterity.com/ciscoiq/sample/

•Internet Protocol Journal is a quarterly journal published by Cisco Systems for engineering

professionals involved in designing, developing, and operating public and private internets and

intranets. You can access the Internet Protocol Journal at this URL:

http://www.cisco.com/ipj

•Networking products offered by Cisco Systems, as well as customer support services, can be

obtained at this URL:

http://www.cisco.com/en/US/products/index.html

•Networking Professionals Connection is an interactive website for networking professionals to share

questions, suggestions, and information about networking products and technologies with Cisco

experts and other networking professionals. Join a discussion at this URL:

http://www.cisco.com/discuss/networking

•World-class networking training is available from Cisco. You can view current offerings at

this URL:

http://www.cisco.com/en/US/learning/index.html

RC-1

Cisco IOS XR Routing Configuration Guide

Implementing BGP on Cisco IOS XR Software

The Border Gateway Protocol (BGP) is an Exterior Gateway Protocol (EGP) that allows you to create

loop-free interdomain routing between autonomous systems. An autonomous system is a set of routers

under a single technical administration. Routers in an autonomous system can use multiple Interior

Gateway Protocols (IGP) to exchange routing information inside the autonomous system and an EGP to

route packets outside the autonomous system.

This module describes information that is unique to BGP for IP Version 4 (IPv4) and IP Version 6 (IPv6)

implementation in Cisco IOS XR Software.

Note For more information about BGP on the Cisco IOS XR software and complete descriptions of the BGP

commands listed in this module, you can see the “Related Documents” section of this module. To locate

documentation for other commands that might appear while executing a configuration task, search online

in the Cisco IOS XR software master command index.

Feature History for Implementing BGP on Cisco IOS XR Configuration Module

Contents

•Prerequisites for Implementing BGP on Cisco IOS XR Software, page RC-2

•Information About Implementing BGP on Cisco IOS XR Software, page RC-2

•How to Implement BGP on Cisco IOS XR Software, page RC-27

•Configuration Examples for Implementing BGP on Cisco IOS XR Software, page RC-76

•Where to Go Next, page RC-79

•Additional References, page RC-80

Release Modification

Release 2.0 This feature was introduced on the Cisco CRS-1.

Release 3.0 No modification.

Release 3.2 Support was added for the Cisco XR 12000 Series Router.

Implementing BGP on Cisco IOS XR Software

Prerequisites for Implementing BGP on Cisco IOS XR Software

RC-2

Cisco IOS XR Routing Configuration Guide

Prerequisites for Implementing BGP on Cisco IOS XR Software

To use this command, you must be in a user group associated with a task group that includes the proper

task IDs. For detailed information about user groups and task IDs, see the Configuring AAA Services on

Cisco IOS XR Software module of the Cisco IOS XR System Security Configuration Guide.

Information About Implementing BGP on Cisco IOS XR Software

To implement BGP, you need to understand the following concepts:

•BGP Functional Overview, page RC-2

•BGP Router Identifier, page RC-3

•BGP Default Limits, page RC-3

•BGP Validation of Local Next-Hop Addresses, page RC-4

•BGP Configuration, page RC-4

•No Default Address Family, page RC-15

•Routing Policy Enforcement, page RC-16

•Update Groups, page RC-18

•BGP Best Path Algorithm, page RC-18

•Multiprotocol BGP, page RC-21

•Route Dampening, page RC-23

•BGP Routing Domain Confederation, page RC-24

•BGP Route Reflectors, page RC-24

•Default Address Family for show Commands, page RC-27

BGP Functional Overview

BGP uses TCP as its transport protocol. Two BGP routers form a TCP connection between one another

(peer routers) and exchange messages to open and confirm the connection parameters.

BGP routers exchange network reachability information. This information is mainly an indication of the

full paths (BGP autonomous system numbers) that a route should take to reach the destination network.

This information helps construct a graph that shows which autonomous systems are loop free and where

routing policies can be applied to enforce restrictions on routing behavior.

Any two routers forming a TCP connection to exchange BGP routing information are called peers or

neighbors. BGP peers initially exchange their full BGP routing tables. After this exchange, incremental

updates are sent as the routing table changes. BGP keeps a version number of the BGP table, which is

the same for all of its BGP peers. The version number changes whenever BGP updates the table due to

routing information changes. Keepalive packets are sent to ensure that the connection is alive between

the BGP peers and notification packets are sent in response to error or special conditions.

Implementing BGP on Cisco IOS XR Software

Information About Implementing BGP on Cisco IOS XR Software

RC-3

Cisco IOS XR Routing Configuration Guide

BGP Router Identifier

For BGP sessions between neighbors to be established, BGP must be assigned a router ID. The router

ID is sent to BGP peers in the OPEN message when a BGP session is established.

BGP attempts to obtain a router ID in the following ways (in order of preference):

•By means of the address configured using the bgp router-id command in router configuration mode.

•By assigning a primary IPv4 address to the interface specified using the bgp router-id command in

router configuration mode.

Note If the specified interface does not have an IPv4 address, or is not up, BGP will fail to obtain a router ID.

•By using the address specified with the router-id command in global configuration mode if the

router is booted with the saved router-id command and if the ID from this command is available

when the last saved loopback configuration is applied.

•By using the primary IPv4 address on the interface specified with the router-id command in global

configuration mode if the box is booted with the saved router-id command in global configuration

mode and if the router ID is up by the time all saved loopback configurations are applied.

•By using the highest IPv4 address on a loopback interface in the system if the router is booted with

saved loopback address configuration.

•By using the primary IPv4 address of the first loopback address that gets configured if there are not

any in the saved configuration.

If none of these methods for obtaining a router ID succeeds, BGP does not have a router ID and cannot

establish any peering sessions with BGP neighbors. In such an instance, an error message is entered in

the system log, and the show bgp summary command displays a router ID of 0.0.0.0.

After BGP has obtained a router ID, it continues to use it even if a better router ID becomes available.

This usage avoids unnecessary flapping for all BGP sessions. However, if the router ID currently in use

becomes invalid (because the interface goes down or its configuration is changed), BGP selects a new

router ID (using the rules described) and all established peering sessions are reset.

We strongly recommend that the bgp router-id command is configured to prevent unnecessary changes

to the router ID (and consequent flapping of BGP sessions).

BGP Default Limits

Cisco IOS XR BGP imposes maximum limits on the number of neighbors that can be configured on the

router and on the maximum number of prefixes that are accepted from a peer for a given address family.

This limitation safeguards the router from resource depletion caused by misconfiguration, either locally

or on the remote neighbor. The following limits apply to BGP configurations:

•The default maximum number of peers that can be configured is 1024. The default can be changed

using the bgp maximum neighbor command. The limit range is 1 to 1500. Any attempt to configure

additional peers beyond the maximum limit or set the maximum limit to a number that is less than

the number of peers currently configured will fail.

•To prevent a peer from flooding BGP with advertisements, a limit is placed on the number of

prefixes that are accepted from a peer for each supported address family. The default limits can be

overridden through configuration of the maximum-prefix limit command for the peer for the

appropriate address family. The following default limits are used if the user does not configure the

maximum number of prefixes for the address family:

Implementing BGP on Cisco IOS XR Software

Information About Implementing BGP on Cisco IOS XR Software

RC-4

Cisco IOS XR Routing Configuration Guide

–

512K (524,288) prefixes for IPv4 unicast.

–

128K (131,072) prefixes for IPv4 multicast.

–

128K (131,072) prefixes for IPv6 unicast.

A cease notification message is sent to the neighbor and the peering with the neighbor is terminated

when the number of prefixes received from the peer for a given address family exceeds the maximum

limit (either set by default or configured by the user) for that address family.

It is possible that the maximum number of prefixes for a neighbor for a given address family has been

configured after the peering with the neighbor has been established and a certain number of prefixes have

already been received from the neighbor for that address family. A cease notification message is sent to

the neighbor and peering with the neighbor is terminated immediately after the configuration if the

configured maximum number of prefixes is fewer than the number of prefixes that have already been

received from the neighbor for the address family.

BGP Validation of Local Next-Hop Addresses

When Cisco IOS XR BGP receives a route advertisement from a neighbor, it validates the next-hop

address contained in the route by verifying that the next-hop address is not the same as an IP address

assigned to an interface on this router (for example, a local address). If the received next-hop address is

a local address, the update is dropped. However, if the next-hop address is set to a local address by the

configured inbound policy, the update is not dropped, is treated as a valid next-hop address, and is

processed normally in Cisco IOS XR BGP. This verification means that the router advertises to its

neighbors that it has a route to the prefix, but any traffic received for that prefix is dropped.

This “blackholing” effect is often used to automatically protect against Denial of Service (DOS) attacks

on user hosts. An inbound policy is configured that sets the next hop to a local address (for example, the

address of a loopback interface) when a route with a particular community is received. When a user finds

that a host is under a DOS attack, a BGP advertisement is sent to the address of the attacked host with

the special community attached. The advertisement causes the Internet service provider (ISP) router to

install a route with a local next hop for that address that drops all traffic destined for it.

BGP Configuration

Cisco IOS XR BGP follows a neighbor-based configuration model that requires that all configurations

for a particular neighbor be grouped in one place under the neighbor configuration. Peer groups are not

supported for either sharing configuration between neighbors or for sharing update messages. The

concept of peer group has been replaced by a set of configuration groups to be used as templates in BGP

configuration and automatically generated update groups to share update messages between neighbors.

BGP configurations are grouped into four major categories:

–

Router Configuration Mode

–

Global Address Family Configuration Mode

–

Neighbor Configuration Mode

–

Neighbor Address Family Configuration Mode

Configuration Modes

The following sections show how to enter each of the configuration modes. From a mode, you can enter

the ? command to display the commands available in that mode.

Implementing BGP on Cisco IOS XR Software

Information About Implementing BGP on Cisco IOS XR Software

RC-5

Cisco IOS XR Routing Configuration Guide

Router Configuration Mode

The following example shows how to enter router configuration mode:

RP/0/RP0/CPU0:router# configuration

RP/0/RP0/CPU0:router(config)# router bgp 140

RP/0/RP0/CPU0:router(config-bgp)#

Global Address Family Configuration Mode

The following example shows how to enter global address family configuration mode:

RP/0/RP0/CPU0:router(config)# router bgp 140

RP/0/RP0/CPU0:router(config-bgp)# address-family ipv4 multicast

RP/0/RP0/CPU0:router(config-bgp-af)#

Neighbor Configuration Mode

The following example shows how to enter neighbor configuration mode:

RP/0/RP0/CPU0:router(config)# router bgp 140

RP/0/RP0/CPU0:router(config-bgp)# neighbor 10.0.0.1

RP/0/RP0/CPU0:router(config-bgp-nbr)#

Neighbor Address Family Configuration Mode

The following example shows how to enter neighbor address family configuration mode:

RP/0/RP0/CPU0:router(config)# router bgp 140

RP/0/RP0/CPU0:router(config-bgp)# neighbor 10.0.0.1

RP/0/RP0/CPU0:router(config-bgp-nbr)# address-family ipv4 unicast

RP/0/RP0/CPU0:router(config-bgp-nbr-af)#

Neighbor Submode

Cisco IOS XR BGP uses a neighbor submode to make it possible to enter configurations without having

to prefix every configuration with the neighbor keyword and the neighbor address:

•Cisco IOS XR software has a submode available for neighbors in which it is not necessary for every

command to have a “neighbor x.x.x.x” prefix.

In Cisco IOS XR software, the configuration is as follows:

Router(config-bgp-af)# neighbor 192.23.1.2

Router(config-bgp-nbr)# remote-as 2002

Router(config-bgp-nbr)# address-family ipv4 multicast

•An address family configuration submode inside the neighbor configuration submode is available

for entering address family-specific neighbor configurations. In Cisco IOS XR, the configuration is

as follows:

Router(config-bgp-af)# neighbor 2002::2

Router(config-bgp-nbr)# remote-as 2002

Router(config-bgp-nbr)# address-family ipv6 unicast

Router(config-bgp-nbr-af)# next-hop-self

Router(config-bgp-nbr-af)# route-policy one in

•You must enter neighbor-specific IPv4 or IPv6 commands in neighbor address-family configuration

submode. In Cisco IOS XR software, the configuration is as follows:

Router(config-bgp)# router bgp 109

Router(config-bgp)# neighbor 192.168.40.24

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Router(config-bgp-nbr)# remote-as 1

Router(config-bgp-nbr)# address-family ipv4 unicast

Router(config-bgp-nbr-af)# maximum-prefix 1000

Configuration Templates

The af-group, session-group, and neighbor-group configuration commands provide template support

for the neighbor configuration in Cisco IOS XR software:

The af-group command is used to group address family-specific neighbor commands within an IPv4 or

IPv6 address family. Neighbors that have the same address family configuration are able to use the

address family group (af-group) name for their address family-specific configuration. A neighbor

inherits the configuration from an address family group by way of the use command. If a neighbor is

configured to use an address family group, the neighbor (by default) inherits the entire configuration

from the address family group. However, a neighbor does not inherit all of the configuration from the

address family group if items are explicitly configured for the neighbor. The address family group

configuration is entered under the BGP router configuration mode. The following example shows how

to enter address family group configuration mode.

RP/0/RP0/CPU0:router(config)# router bgp 140

RP/0/RP0/CPU0:router(config-bgp)# af-group afmcast1 address-family ipv4 multicast

RP/0/RP0/CPU0:router(config-bgp-afgrp)#

The session-group command allows you to create a session group from which neighbors can inherit

address family-independent configuration. A neighbor inherits the configuration from a session group

by way of the use command. If a neighbor is configured to use a session group, the neighbor (by default)

inherits the entire configuration of the session group. A neighbor does not inherit all of the configuration

from a session group if a configuration is done directly on that neighbor. The following example shows

how to enter session group configuration mode:

RP/0/RP0/CPU0:router(config)# router bgp 140

RP/0/RP0/CPU0:router(config-bgp)# session-group session1

RP/0/RP0/CPU0:router(config-bgp-sngrp)#

The neighbor-group command helps you apply the same configuration to one or more neighbors.

Neighbor groups can include session groups and address family groups and can comprise the complete

configuration for a neighbor. After a neighbor group is configured, a neighbor can inherit the

configuration of the group using the use command. If a neighbor is configured to use a neighbor group,

the neighbor inherits the entire BGP configuration of the neighbor group.

The following example shows how to enter neighbor group configuration mode:

RP/0/RP0/CPU0:router(config)# router bgp 140

RP/0/RP0/CPU0:router(config-bgp)# neighbor-group nbrgroup1

RP/0/RP0/CPU0:router(config-bgp-nbrgrp)#

The following example shows how to enter neighbor group address family configuration mode:

RP/0/RP0/CPU0:router(config)# router bgp 140

RP/0/RP0/CPU0:router(config-bgp)# neighbor-group nbrgroup1

RP/0/RP0/CPU0:router(config-bgp-nbrgrp)# address-family ipv4 unicast

RP/0/RP0/CPU0:router(config-bgp-nbrgrp-af)#

•However, a neighbor does not inherit all of the configuration from the neighbor group if items are

explicitly configured for the neighbor. In addition, some part of the configuration of the neighbor

group could be hidden if a session group or address family group was also being used.

Configuration grouping has the following effects in Cisco IOS XR software:

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•Commands entered at the session group level define address family-independent commands (the

same commands as in the neighbor submode).

•Commands entered at the address family group level define address family-dependent commands

for a specified address family (the same commands as in the neighbor-address family configuration

submode).

•Commands entered at the neighbor group level define address family-independent commands and

address family-dependent commands for each address family (the same as all available neighbor

commands), and define the use command for the address family group and session group commands.

Template Inheritance Rules

In Cisco IOS XR software, BGP neighbors or groups inherit configuration from other configuration

groups.

For address family-independent configurations:

•Neighbors can inherit from session groups and neighbor groups.

•Neighbor groups can inherit from session groups and other neighbor groups.

•Session groups can inherit from other session groups.

•If a neighbor uses a session group and a neighbor group, the configurations in the session group are

preferred over the global address family configurations in the neighbor group.

For address family-dependent configurations:

•Address family groups can inherit from other address family groups.

•Neighbor groups can inherit from address family groups and other neighbor groups.

•Neighbors can inherit from address family groups and neighbor groups.

Configuration group inheritance rules are numbered in order of precedence as follows:

1. If the item is configured directly on the neighbor, that value is used. In the example that follows, the

advertisement interval is configured both on the neighbor group and neighbor configuration and the

advertisement interval being used is from the neighbor configuration:

RP/0/RP0/CPU0:router(config)# router bgp 140

RP/0/RP0/CPU0:router(config-bgp)# neighbor-group AS_1

RP/0/RP0/CPU0:router(config-bgp-nbrgrp)# advertisement-interval 15

RP/0/RP0/CPU0:router(config-bgp-nbrgrp)# exit

RP/0/RP0/CPU0:router(config-bgp)# neighbor 10.1.1.1

RP/0/RP0/CPU0:router(config-bgp-nbr)# remote-as 1

RP/0/RP0/CPU0:router(config-bgp-nbr)# use neighbor-group AS_1

RP/0/RP0/CPU0:router(config-bgp-nbr)# advertisement-interval 20

The following output from the show bgp neighbors command shows that the advertisement interval

used is 20 seconds:

RP/0/RP0/CPU0:router# show bgp neighbors 10.1.1.1

BGP neighbor is 10.1.1.1, remote AS 1, local AS 140, external link

Remote router ID 0.0.0.0

BGP state = Idle

Last read 00:00:00, hold time is 180, keepalive interval is 60 seconds

Received 0 messages, 0 notifications, 0 in queue

Sent 0 messages, 0 notifications, 0 in queue

Minimum time between advertisement runs is 20 seconds

For Address Family: IPv4 Unicast

BGP neighbor version 0

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Update group: 0.1

eBGP neighbor with no inbound or outbound policy; defaults to 'drop'

Route refresh request: received 0, sent 0

0 accepted prefixes

Prefix advertised 0, suppressed 0, withdrawn 0, maximum limit 524288

Threshold for warning message 75%

Connections established 0; dropped 0

Last reset 00:00:14, due to BGP neighbor initialized

External BGP neighbor not directly connected.

2. Otherwise, if the neighbor uses a session group or address family group, the configuration value is

obtained from the session group or address family group. If the address family group or session

group has a parent and an item is configured on the parent, the parent configuration is used. If the

item is not configured on the parent, but is configured on the parent ‘s parent, the configuration of

the parent’s parent is used, and so on. In the example that follows, the advertisement interval is

configured on a neighbor group and a session group and the advertisement interval value being used

is from the session group:

RP/0/RP0/CPU0:router(config)# router bgp 140

RP/0/RP0/CPU0:router(config-bgp)# session-group AS_2

RP/0/RP0/CPU0:router(config-bgp-sngrp)# advertisement-interval 15

RP/0/RP0/CPU0:router(config-bgp-sngrp)# exit

RP/0/RP0/CPU0:router(config-bgp)# neighbor-group AS_1

RP/0/RP0/CPU0:router(config-bgp-nbrgrp)# advertisement-interval 20

RP/0/RP0/CPU0:router(config-bgp-nbrgrp)# exit

RP/0/RP0/CPU0:router(config-bgp)# neighbor 192.168.0.1

RP/0/RP0/CPU0:router(config-bgp-nbr)# remote-as 1

RP/0/RP0/CPU0:router(config-bgp-nbr)# use session-group AS_2

RP/0/RP0/CPU0:router(config-bgp-nbr)# use neighbor-group AS_1

The following output from the show bgp neighbors command shows that the advertisement interval

used is 15 seconds:

RP/0/RP0/CPU0:router# show bgp neighbors 192.168.0.1

BGP neighbor is 192.168.0.1, remote AS 1, local AS 140, external link

Remote router ID 0.0.0.0

BGP state = Idle

Last read 00:00:00, hold time is 180, keepalive interval is 60 seconds

Received 0 messages, 0 notifications, 0 in queue

Sent 0 messages, 0 notifications, 0 in queue

Minimum time between advertisement runs is 15 seconds

For Address Family: IPv4 Unicast

BGP neighbor version 0

Update group: 0.1

eBGP neighbor with no inbound or outbound policy; defaults to 'drop'

Route refresh request: received 0, sent 0

0 accepted prefixes

Prefix advertised 0, suppressed 0, withdrawn 0, maximum limit 524288

Threshold for warning message 75%

Connections established 0; dropped 0

Last reset 00:03:23, due to BGP neighbor initialized

External BGP neighbor not directly connected.

3. Otherwise, if the neighbor uses a neighbor group and does not use a session group or address family

group, the configuration value can be obtained from the neighbor group either directly or through

inheritance. In the example that follows, the advertisement interval from the neighbor group is used

because it is not configured directly on the neighbor and no session group is used:

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RP/0/RP0/CPU0:router(config)# router bgp 150

RP/0/RP0/CPU0:router(config-bgp)# session-group AS_2

RP/0/RP0/CPU0:router(config-bgp-sngrp)# advertisement-interval 20

RP/0/RP0/CPU0:router(config-bgp-sngrp)# exit

RP/0/RP0/CPU0:router(config-bgp)# neighbor-group AS_1

RP/0/RP0/CPU0:router(config-bgp-nbrgrp)# advertisement-interval 15

RP/0/RP0/CPU0:router(config-bgp-nbrgrp)# exit

RP/0/RP0/CPU0:router(config-bgp)# neighbor 192.168.1.1

RP/0/RP0/CPU0:router(config-bgp-nbr)# remote-as 1

RP/0/RP0/CPU0:router(config-bgp-nbr)# use neighbor-group AS_1

The following output from the show bgp neighbors command shows that the advertisement interval

used is 15 seconds:

RP/0/RP0/CPU0:router# show bgp neighbors 192.168.1.1

BGP neighbor is 192.168.2.2, remote AS 1, local AS 140, external link

Remote router ID 0.0.0.0

BGP state = Idle

Last read 00:00:00, hold time is 180, keepalive interval is 60 seconds

Received 0 messages, 0 notifications, 0 in queue

Sent 0 messages, 0 notifications, 0 in queue

Minimum time between advertisement runs is 15 seconds

For Address Family: IPv4 Unicast

BGP neighbor version 0

Update group: 0.1

eBGP neighbor with no outbound policy; defaults to 'drop'

Route refresh request: received 0, sent 0

Inbound path policy configured

Policy for incoming advertisements is POLICY_1

0 accepted prefixes

Prefix advertised 0, suppressed 0, withdrawn 0, maximum limit 524288

Threshold for warning message 75%

Connections established 0; dropped 0

Last reset 00:01:14, due to BGP neighbor initialized

External BGP neighbor not directly connected.

To illustrate the same rule, the following example shows how to set the advertisement interval to 15

(from the session group). The timers are set to the default (60/180) because the neighbor uses a

session group, thus hiding the timers command in the neighbor group. The inbound policy is set to

POLICY_1 from the neighbor group.

RP/0/RP0/CPU0:router(config)# router bgp 140

RP/0/RP0/CPU0:router(config-bgp)# session-group ADV

RP/0/RP0/CPU0:router(config-bgp-sngrp)# advertisement-interval 15

RP/0/RP0/CPU0:router(config-bgp-sngrp)# exit

RP/0/RP0/CPU0:router(config-bgp)# neighbor-group TIMER

RP/0/RP0/CPU0:router(config-bgp-nbrgrp)# timers 10 30

RP/0/RP0/CPU0:router(config-bgp-nbrgrp)# address-family ipv4 unicast

RP/0/RP0/CPU0:router(config-bgp-nbrgrp)# route-policy POLICY_1 in

RP/0/RP0/CPU0:router(config-bgp-nbrgrp)# exit

RP/0/RP0/CPU0:router(config-bgp)# exit

RP/0/RP0/CPU0:router(config-bgp)# neighbor 192.168.2.2

RP/0/RP0/CPU0:router(config-bgp-nbr)# remote-as 1

RP/0/RP0/CPU0:router(config-bgp-nbr)# use session-group ADV

RP/0/RP0/CPU0:router(config-bgp-nbr)# use neighbor-group TIMER

The following output from the show bgp neighbors command shows that the advertisement interval

used is 15 seconds:

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RP/0/RP0/CPU0:router# show bgp neighbors 192.168.2.2

BGP neighbor is 192.168.2.2, remote AS 1, local AS 140, external link

Remote router ID 0.0.0.0

BGP state = Idle

Last read 00:00:00, hold time is 180, keepalive interval is 60 seconds

Received 0 messages, 0 notifications, 0 in queue

Sent 0 messages, 0 notifications, 0 in queue

Minimum time between advertisement runs is 15 seconds

For Address Family: IPv4 Unicast

BGP neighbor version 0

Update group: 0.1

eBGP neighbor with no inbound or outbound policy; defaults to 'drop'

Route refresh request: received 0, sent 0

0 accepted prefixes

Prefix advertised 0, suppressed 0, withdrawn 0, maximum limit 524288

Threshold for warning message 75%

Connections established 0; dropped 0

Last reset 00:02:03, due to BGP neighbor initialized

External BGP neighbor not directly connected.

4. Otherwise, the default value is used. In the example that follows, neighbor 10.0.101.5 has the

minimum time between advertisement runs set to 30 seconds (default) because the neighbor is not

configured to use the neighbor configuration or the neighbor group configuration:

RP/0/RP0/CPU0:router(config)# router bgp 140

RP/0/RP0/CPU0:router(config-bgp)# neighbor-group AS_1

RP/0/RP0/CPU0:router(config-bgp-nbrgrp)# remote-as 1

RP/0/RP0/CPU0:router(config-bgp-nbrgrp)# exit

RP/0/RP0/CPU0:router(config-bgp-nbrgrp)# neighbor-group adv_15

RP/0/RP0/CPU0:router(config-bgp-nbrgrp)# remote-as 10

RP/0/RP0/CPU0:router(config-bgp-nbrgrp)# advertisement-interval 15

RP/0/RP0/CPU0:router(config-bgp-nbrgrp)# exit

RP/0/RP0/CPU0:router(config-bgp)# neighbor 10.0.101.5

RP/0/RP0/CPU0:router(config-bgp-nbr)# use neighbor-group AS_1

RP/0/RP0/CPU0:router(config-bgp-nbr)# exit

RP/0/RP0/CPU0:router(config-bgp)# neighbor 10.0.101.10

RP/0/RP0/CPU0:router(config-bgp-nbr)# use neighbor-group adv_15

The following output from the show bgp neighbors command shows that the advertisement interval

used is 30 seconds:

RP/0/RP0/CPU0:router# show bgp neighbors 10.0.101.5

BGP neighbor is 10.0.101.5, remote AS 1, local AS 140, external link

Remote router ID 0.0.0.0

BGP state = Idle

Last read 00:00:00, hold time is 180, keepalive interval is 60 seconds

Received 0 messages, 0 notifications, 0 in queue

Sent 0 messages, 0 notifications, 0 in queue

Minimum time between advertisement runs is 30 seconds

For Address Family: IPv4 Unicast

BGP neighbor version 0

Update group: 0.2

eBGP neighbor with no inbound or outbound policy; defaults to 'drop'

Route refresh request: received 0, sent 0

0 accepted prefixes

Prefix advertised 0, suppressed 0, withdrawn 0, maximum limit 524288

Threshold for warning message 75%

Connections established 0; dropped 0

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Last reset 00:00:25, due to BGP neighbor initialized

External BGP neighbor not directly connected.

The inheritance rules used when groups are inheriting configuration from other groups are the same

as the rules given for neighbors inheriting from groups.

Template Inheritance

You can use the following show commands described to monitor BGP inheritance information:

•show bgp neighbors, page RC-11

•show bgp af-group, page RC-12

•show bgp session-group, page RC-13

•show bgp neighbor-group, page RC-14

show bgp neighbors

Use the show bgp neighbors command to display information about the BGP configuration for

neighbors.

•Use the configuration keyword to display the effective configuration for the neighbor, including any

settings that have been inherited from session groups, neighbor groups, or address family groups

used by this neighbor.

•Use the inheritance keyword to display the session groups, neighbor groups, and address family

groups from which this neighbor is capable of inheriting configuration .

The show bgp neighbors command examples that follow are based on the sample configuration:

RP/0/RP0/CPU0:router(config)# router bgp 140

RP/0/RP0/CPU0:router(config-bgp)# af-group GROUP_3 address-family ipv4 unicast

RP/0/RP0/CPU0:router(config-bgp-afgrp)# next-hop-self

RP/0/RP0/CPU0:router(config-bgp-afgrp)# route-policy POLICY_1 in

RP/0/RP0/CPU0:router(config-bgp0afgrp)# exit

RP/0/RP0/CPU0:router(config-bgp)# session-group GROUP_2

RP/0/RP0/CPU0:router(config-bgp-sngrp)# advertisement-interval 15

RP/0/RP0/CPU0:router(config-bgp-sngrp)# exit

RP/0/RP0/CPU0:router(config-bgp)# neighbor-group GROUP_1

RP/0/RP0/CPU0:router(config-bgp-nbrgrp)# use session-group GROUP_2

RP/0/RP0/CPU0:router(config-bgp-nbrgrp)# ebgp-multihop 3

RP/0/RP0/CPU0:router(config-bgp-nbrgrp)# address-family ipv4 unicast

RP/0/RP0/CPU0:router(config-bgp-nbrgrp-af)# weight 100

RP/0/RP0/CPU0:router(config-bgp-nbrgrp-af)# send-community-ebgp

RP/0/RP0/CPU0:router(config-bgp-nbrgrp-af)# exit

RP/0/RP0/CPU0:router(config-bgp-nbrgrp)# address-family ipv4 multicast

RP/0/RP0/CPU0:router(config-bgp-nbrgrp-af)# default-originate

RP/0/RP0/CPU0:router(config-bgp-nbrgrp-af)# exit

RP/0/RP0/CPU0:router(config-bgp-nbrgrp)# exit

RP/0/RP0/CPU0:router(config-bgp)# neighbor 192.168.0.1

RP/0/RP0/CPU0:router(config-bgp-nbr)# remote-as 2

RP/0/RP0/CPU0:router(config-bgp-nbr)# use neighbor-group GROUP_1

RP/0/RP0/CPU0:router(config-bgp-nbr)# address-family ipv4 unicast

RP/0/RP0/CPU0:router(config-bgp-nbr-af)# use af-group GROUP_3

RP/0/RP0/CPU0:router(config-bgp-nbr-af)# weight 200

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The following example displays sample output from the show bgp neighbors command using the

inheritance keyword. The example shows that the neighbor inherits session parameters from neighbor

group GROUP_1, which in turn inherits from session group GROUP_2. The neighbor inherits IPv4

unicast parameters from address family group GROUP_3 and IPv4 multicast parameters from neighbor

group GROUP_1:

RP/0/RP0/CPU0:router# show bgp neighbors 192.168.0.1 inheritance

Session: n:GROUP_1 s:GROUP_2

IPv4 Unicast: a:GROUP_3

IPv4 Multicast: n:GROUP_1

The following example displays sample output from the show bgp neighbors command using the

configuration keyword. The example shows from where each item of configuration was inherited, or if

it was configured directly on the neighbor (indicated by [ ]). For example, the ebgp-multihop 3

command was inherited from neighbor group GROUP_1 and the next-hop-self command was inherited

from the address family group GROUP_3:

RP/0/RP0/CPU0:router# show bgp neighbors 192.168.0.1 configuration

neighbor 192.168.0.1

remote-as 2 []

advertisement-interval 15 [n:GROUP_1 s:GROUP_2]

ebgp-multihop 3 [n:GROUP_1]

address-family ipv4 unicast []

next-hop-self [a:GROUP_3]

route-policy POLICY_1 in [a:GROUP_3]

weight 200 []

address-family ipv4 multicast [n:GROUP_1]

default-originate [n:GROUP_1]

show bgp af-group

Use the show bgp af-group command to display address family groups:

•Use the configuration keyword to display the effective configuration for the address family group,

including any settings that have been inherited from address family groups used by this address

family group.

•Use the inheritance keyword to display the address family groups from which this address family

group is capable of inheriting configuration.

•Use the users keyword to display the neighbors, neighbor groups, and address family groups that

inherit configuration from this address family group.

The show bgp af-group command examples that follow are based on the this sample configuration:

RP/0/RP0/CPU0:router(config)# router bgp 140

RP/0/RP0/CPU0:router(config-bgp)# af-group GROUP_3 address-family ipv4 unicast

RP/0/RP0/CPU0:router(config-bgp-afgrp)# remove-private-as

RP/0/RP0/CPU0:router(config-bgp-afgrp)# route-policy POLICY_1 in

RP/0/RP0/CPU0:router(config-bgp-afgrp)# exit

RP/0/RP0/CPU0:router(config-bgp)# af-group GROUP_1 address-family ipv4 unicast

RP/0/RP0/CPU0:router(config-bgp-afgrp)# use af-group GROUP_2

RP/0/RP0/CPU0:router(config-bgp-afgrp)# maximum-prefix 2500 75 warning-only

RP/0/RP0/CPU0:router(config-bgp-afgrp)# default-originate

RP/0/RP0/CPU0:router(config-bgp-afgrp)# exit

RP/0/RP0/CPU0:router(config-bgp)# af-group GROUP_2 address-family ipv4 unicast

RP/0/RP0/CPU0:router(config-bgp-afgrp)# use af-group GROUP_3

RP/0/RP0/CPU0:router(config-bgp-afgrp)# send-community-ebgp

RP/0/RP0/CPU0:router(config-bgp-afgrp)# send-extended-community-ebgp

RP/0/RP0/CPU0:router(config-bgp-afgrp)# capability orf prefix-list both

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The following example displays sample output from the show bgp af-group command using the

configuration keyword. This example shows from where each configuration item was inherited. The

default-originate command was configured directly on this address family group (indicated by [ ]). The

remove-private-as command was inherited from address family group GROUP_2, which in turn

inherited from address family group GROUP_3:

RP/0/RP0/CPU0:router# show bgp af-group GROUP_1 configuration

af-group GROUP_1 address-family ipv4 unicast

capability orf prefix-list both [a:GROUP_2]

default-originate []

maximum-prefix 2500 75 warning-only []

route-policy POLICY_1 in [a:GROUP_2 a:GROUP_3]

remove-private-AS [a:GROUP_2 a:GROUP_3]

send-community-ebgp [a:GROUP_2]

send-extended-community-ebgp [a:GROUP_2]

The following example displays sample output from the show bgp af-group command using the users

keyword:

RP/0/RP0/CPU0:router# show bgp af-group GROUP_2 users

IPv4 Unicast: a:GROUP_1

The following example displays sample output from the show bgp af-group command using the

inheritance keyword. This shows that the specified address family group GROUP_1 directly uses the

GROUP_2 address family group, which in turn uses the GROUP_3 address family group:

RP/0/RP0/CPU0:router# show bgp af-group GROUP_1 inheritance

IPv4 Unicast: a:GROUP_2 a:GROUP_3

show bgp session-group

Use the show bgp session-group command to display session groups:

•Use the configuration keyword to display the effective configuration for the session group,

including any settings that have been inherited from session groups used by this session group.

•Use the inheritance keyword to display the session groups from which this session group is capable

of inheriting configuration.

•Use the users keyword to display the session groups, neighbor groups, and neighbors that inherit

configuration from this session group.

The examples that follow sample output from the show bgp session-group command with the

configuration keyword in EXEC mode. The examples are based on the following session group

configuration:

RP/0/RP0/CPU0:router(config)# router bgp 140

RP/0/RP0/CPU0:router(config-bgp)# session-group GROUP_1

RP/0/RP0/CPU0:router(config-bgp-sngrp)# use session-group GROUP_2

RP/0/RP0/CPU0:router(config-bgp-sngrp)# update-source Loopback 0

RP/0/RP0/CPU0:router(config-bgp-sngrp)# exit

RP/0/RP0/CPU0:router(config-bgp)# session-group GROUP_2

RP/0/RP0/CPU0:router(config-bgp-sngrp)# use session-group GROUP_3

RP/0/RP0/CPU0:router(config-bgp-sngrp)# ebgp-multihop 2

RP/0/RP0/CPU0:router(config-bgp-sngrp)# exit

RP/0/RP0/CPU0:router(config-bgp)# session-group GROUP_3

RP/0/RP0/CPU0:router(config-bgp-sngrp)# dmz-link-bandwidth

The following is sample output from the show bgp session-group command with the configuration

keyword in EXEC mode:

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RP/0/RP0/CPU0:router# show bgp session-group GROUP_1 configuration

session-group GROUP_1

ebgp-multihop 2 [s:GROUP_2]

update-source Loopback0 []

dmz-link-bandwidth [s:GROUP_2 s:GROUP_3]

The following is sample output from the show bgp session-group command with the inheritance

keyword showing that the GROUP_1 session group inherits session parameters from the GROUP_3 and

GROUP_2 session groups:

RP/0/RP0/CPU0:router# show bgp session-group GROUP_1 inheritance

Session: s:GROUP_2 s:GROUP_3

The following is sample output from the show bgp session-group command with the users keyword

showing that both the GROUP_1 and GROUP_2 session groups inherit session parameters from the

GROUP_3 session group:

RP/0/RP0/CPU0:router# show bgp session-group GROUP_3 users

Session: s:GROUP_1 s:GROUP_2

show bgp neighbor-group

Use the show bgp neighbor-group command to display neighbor groups:

•Use the configuration keyword to display the effective configuration for the neighbor group,

including any settings that have been inherited from neighbor groups used by this neighbor group.

•Use the inheritance keyword to display the address family groups, session groups, and neighbor

groups from which this neighbor group is capable of inheriting configuration.

•Use the users keyword to display the neighbors and neighbor groups that inherit configuration from

this neighbor group.

The examples are based on the following group configuration:

RP/0/RP0/CPU0:router(config)# router bgp 140

RP/0/RP0/CPU0:router(config-bgp)# af-group GROUP_3 address-family ipv4 unicast

RP/0/RP0/CPU0:router(config-bgp-afgrp)# remove-private-as

RP/0/RP0/CPU0:router(config-bgp-afgrp)# soft-reconfiguration inbound

RP/0/RP0/CPU0:router(config-bgp-afgrp)# exit

RP/0/RP0/CPU0:router(config-bgp)# af-group GROUP_2 address-family ipv4 unicast

RP/0/RP0/CPU0:router(config-bgp-afgrp)# use af-group GROUP_3

RP/0/RP0/CPU0:router(config-bgp-afgrp)# send-community-ebgp

RP/0/RP0/CPU0:router(config-bgp-afgrp)# send-extended-community-ebgp

RP/0/RP0/CPU0:router(config-bgp-afgrp)# capability orf prefix-list both

RP/0/RP0/CPU0:router(config-bgp-afgrp)# exit

RP/0/RP0/CPU0:router(config-bgp)# session-group GROUP_3

RP/0/RP0/CPU0:router(config-bgp-sngrp)# timers 30 90

RP/0/RP0/CPU0:router(config-bgp-sngrp)# exit

RP/0/RP0/CPU0:router(config-bgp)# neighbor-group GROUP_1

RP/0/RP0/CPU0:router(config-bgp-nbrgrp)# remote-as 1982

RP/0/RP0/CPU0:router(config-bgp-nbrgrp)# use neighbor-group GROUP_2

RP/0/RP0/CPU0:router(config-bgp-nbrgrp)# address-family ipv4 unicast

RP/0/RP0/CPU0:router(config-bgp-nbrgrp-af)# exit

RP/0/RP0/CPU0:router(config-nbrgrp)# exit

RP/0/RP0/CPU0:router(config-bgp)# neighbor-group GROUP_2

RP/0/RP0/CPU0:router(config-bgp-nbrgrp)# use session-group GROUP_3

RP/0/RP0/CPU0:router(config-bgp-nbrgrp)# address-family ipv4 unicast

RP/0/RP0/CPU0:router(config-bgp-nbrgrp-af)# use af-group GROUP_2

RP/0/RP0/CPU0:router(config-bgp-nbrgrp-af)# weight 100

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The following is sample output from the show bgp neighbor-group command with the configuration

keyword. The configuration setting source is shown to the right of each command. In the output shown

previously, the remote autonomous system is configured directly on neighbor group GROUP_1, and the

send community setting is inherited from neighbor group GROUP_2, which in turn inherits the setting

from address family group GROUP_3:

RP/0/RP0/CPU0:router# show bgp neighbor-group GROUP_1 configuration

neighbor-group GROUP_1

remote-as 1982 []

timers 30 90 [n:GROUP_2 s:GROUP_3]

address-family ipv4 unicast []

capability orf prefix-list both [n:GROUP_2 a:GROUP_2]

remove-private-AS [n:GROUP_2 a:GROUP_2 a:GROUP_3]

send-community-ebgp [n:GROUP_2 a:GROUP_2]

send-extended-community-ebgp [n:GROUP_2 a:GROUP_2]

soft-reconfiguration inbound [n:GROUP_2 a:GROUP_2 a:GROUP_3]

weight 100 [n:GROUP_2]

The following is sample output from the show bgp neighbor-group command with the inheritance

keyword. This output shows that the specified neighbor group GROUP_1 inherits session (address

family-independent) configuration parameters from neighbor group GROUP_2. Neighbor group

GROUP_2 inherits its session parameters from session group GROUP_3. It also shows that the

GROUP_1 neighbor group inherits IPv4 unicast configuration parameters from the GROUP_2 neighbor

group, which in turn inherits them from the GROUP_2 address family group, which itself inherits them

from the GROUP_3 address family group:

RP/0/RP0/CPU0:router# show bgp neighbor-group GROUP_1 inheritance

Session: n:GROUP-2 s:GROUP_3

IPv4 Unicast: n:GROUP_2 a:GROUP_2 a:GROUP_3

The following is sample output from the show bgp neighbor-group command with the users keyword.

This output shows that the GROUP_1 neighbor group inherits session (address family-independent)

configuration parameters from the GROUP_2 neighbor group. The GROUP_1 neighbor group also

inherits IPv4 unicast configuration parameters from the GROUP_2 neighbor group:

RP/0/RP0/CPU0:router# show bgp neighbor-group GROUP_2 users

Session: n:GROUP_1

IPv4 Unicast: n:GROUP_1

No Default Address Family

BGP does not support the concept of a default address family. An address family must be explicitly

configured under the BGP router configuration for the address family to be activated in BGP. Similarly,

an address family must be explicitly configured under a neighbor for the BGP session to be activated

under that address family. It is not required to have any address family configured under the BGP router

configuration level for a neighbor to be configured. However, it is a requirement to have an address

family configured at the BGP router configuration level for the address family to be configured under a

neighbor.

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Routing Policy Enforcement

External BGP (eBGP) neighbors must have an inbound and outbound policy configured. If no policy is

configured, no routes are accepted from the neighbor, nor are any routes advertised to it. This added

security measure ensures that routes cannot accidentally be accepted or advertised in the case of a

configuration omission error.

Note This enforcement affects only eBGP neighbors (neighbors in a different autonomous system than this

router). For internal BGP (iBGP) neighbors (neighbors in the same autonomous system), all routes are

accepted or advertised if there is no policy.

In the following example, for an eBGP neighbor, if all routes should be accepted and advertised with no

modifications, a simple pass-all policy is configured:

RP/0/RP0/CPU0:router(config)# route-policy pass-all

RP/0/RP0/CPU0:router(config-rpl)# pass

RP/0/RP0/CPU0:router(config-rpl)# end-policy

RP/0/RP0/CPU0:router(config)# commit

Use the route-policy (BGP) command in the neighbor address-family configuration mode to apply the

pass-all policy to a neighbor. The following example shows how to allow all IPv4 unicast routes to be

received from neighbor 192.168.40.42 and advertise all IPv4 unicast routes back to it:

RP/0/RP0/CPU0:router(config)# router bgp 1

RP/0/RP0/CPU0:router(config-bgp)# neighbor 192.168.40.24

RP/0/RP0/CPU0:router(config-bgp-nbr)# remote-as 2

RP/0/RP0/CPU0:router(config-bgp-nbr)# address-family ipv4 unicast

RP/0/RP0/CPU0:router(config-bgp-nbr-af)# route-policy pass-all in

RP/0/RP0/CPU0:router(config-bgp-nbr-af)# route-policy pass-all out

RP/0/RP0/CPU0:router(config-bgp-nbr-af)# commit

Use the show bgp summary command to display eBGP neighbors that do not have both an inbound and

outbound policy for every active address family. In the following example, such eBGP neighbors are

indicated in the output with an exclamation (!) mark:

RP/0/RP0/CPU0:router# show bgp all all summary

Address Family: IPv4 Unicast

============================

BGP router identifier 10.0.0.1, local AS number 1

BGP generic scan interval 60 secs

BGP main routing table version 41

BGP scan interval 60 secs

BGP is operating in STANDALONE mode.

Process RecvTblVer bRIB/RIB SendTblVer

Speaker 41 41 41

Neighbor Spk AS MsgRcvd MsgSent TblVer InQ OutQ Up/Down St/PfxRcd

10.0.101.1 0 1 919 925 41 0 0 15:15:08 10

10.0.101.2 0 2 0 0 0 0 0 00:00:00 Idle

Address Family: IPv4 Multicast

==============================

BGP router identifier 10.0.0.1, local AS number 1

BGP generic scan interval 60 secs

BGP main routing table version 1

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BGP scan interval 60 secs

BGP is operating in STANDALONE mode.

Process RecvTblVer bRIB/RIB SendTblVer

Speaker 1 1 1

Some configured eBGP neighbors do not have both inbound and

outbound policies configured for IPv4 Multicast address family.

These neighbors will default to sending and/or receiving no

routes and are marked with ’!’ in the output below. Use the

’show bgp neighbor <nbr_address>’ command for details.

Neighbor Spk AS MsgRcvd MsgSent TblVer InQ OutQ Up/Down St/PfxRcd

10.0.101.2 0 2 0 0 0 0 0 00:00:00 Idle!

Address Family: IPv6 Unicast

============================

BGP router identifier 10.0.0.1, local AS number 1

BGP generic scan interval 60 secs

BGP main routing table version 2

BGP scan interval 60 secs

BGP is operating in STANDALONE mode.

Process RecvTblVer bRIB/RIB SendTblVer

Speaker 2 2 2

Neighbor Spk AS MsgRcvd MsgSent TblVer InQ OutQ Up/Down St/PfxRcd

2222::2 0 2 920 918 2 0 0 15:15:11 1

2222::4 0 3 0 0 0 0 0 00:00:00 Idle

Address Family: IPv6 Multicast

==============================

BGP router identifier 10.0.0.1, local AS number 1

BGP generic scan interval 60 secs

BGP main routing table version 1

BGP scan interval 60 secs

BGP is operating in STANDALONE mode.

Process RecvTblVer bRIB/RIB SendTblVer

Speaker 1 1 1

Some configured eBGP neighbors do not have both inbound and

outbound policies configured for IPv6 Multicast address family.

These neighbors will default to sending and/or receiving no

routes and are marked with ’!’ in the output below. Use the

’show bgp neighbor <nbr_address>’ command for details.

Neighbor Spk AS MsgRcvd MsgSent TblVer InQ OutQ Up/Down St/PfxRcd

2222::2 0 2 920 918 0 0 0 15:15:11 0

2222::4 0 3 0 0 0 0 0 00:00:00 Idle!

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Table Policy

The table policy feature in BGP allows you to configure traffic index values on routes as they are

installed in the global routing table. This feature is enabled using the table-policy command and

supports the BGP policy accounting feature.

BGP policy accounting uses traffic indices that are set on BGP routes to track various counters. See

Implementing Routing Policy on Cisco IOS XR Software for details on table policy use. See the Cisco

Express Forwarding Commands on Cisco IOS XR Software module in the Cisco IOS XR IP Addresses

and Services Command Reference for details on BGP policy accounting.

Table policy also provides the ability to drop routes from the RIB based on match criteria. This feature

can be useful in certain applications and should be used with caution as it can easily create a routing

‘black-hole’ where BGP advertises routes to neighbors that BGP does not install in its global routing

table but in the forwarding table .

Update Groups

The BGP Update Groups feature contains an algorithm that dynamically calculates and optimizes update

groups of neighbors that share outbound policies and can share the update messages. The BGP Update

Groups feature separates update group replication from peer group configuration, improving

convergence time and flexibility of neighbor configuration.

To use this feature, you must understand the following concepts:

•BGP Update Generation and Update Groups, page RC-18

•BGP Update Group, page RC-18

BGP Update Generation and Update Groups

The BGP Update Groups feature separates BGP update generation from neighbor configuration. The

BGP Update Groups feature introduces an algorithm that dynamically calculates BGP update group

membership based on outbound routing policies. This feature does not require any configuration by the

network operator. Update group-based message generation occurs automatically and independently.

BGP Update Group

When a change to the configuration occurs, the router automatically recalculates update group

memberships and applies the changes.

For the best optimization of BGP update group generation, we recommend that the network operator

keeps outbound routing policy the same for neighbors that have similar outbound policies. This feature

contains commands for monitoring BGP update groups. For more information about the commands, see

the “Monitoring BGP Update Groups” section on page RC-75.

BGP Best Path Algorithm

BGP routers typically receive multiple paths to the same destination. The BGP best path algorithm

determines the best path to install in the IP routing table and to use for forwarding traffic. This section

describes the IOS XR implementation of BGP best path algorithm, as specified in Section 9.1 of the

Internet Engineering Task Force (IETF) Network Working Group draft-ietf-idr-bgp4-24.txt document.

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The BGP best path algorithm implementation is in three parts:

•Part 1—Compares two paths to determine which is better.

•Part 2—Iterates over all paths and determines which order to compare the paths to select the overall

best path.

•Part 3—Determines whether the old and new best paths differ enough so that the new best path

should be used.

Note The order of comparison determined by Part 2 is important because the comparison operation is not

transitive; that is, if three paths, A, B, and C exist, such that when A and B are compared, A is better,

and when B and C are compared, B is better, it is not necessarily the case that when A and C are

compared, A is better. This nontransitivity arises because the multi exit discriminator (MED) is

compared only among paths from the same neighboring autonomous system (AS) and not among all

paths.

Comparing Pairs of Paths

The following steps are completed to compare two paths and determine the better path:

1. If either path is invalid (for example, it has the maximum possible MED value, or it has an

unreachable nexthop), then the other path is chosen (provided that the path is valid).

2. If the paths have unequal weights, the path with the highest weight is chosen. Note: the weight is

entirely local to the router, and can be set with the weight command or using a routing policy.

3. If the paths have unequal local preferences, the path with the higher local preference is chosen. Note:

If a local preference attribute was received with the path or was set by a routing policy, then that

value is used in this comparison. Otherwise, the default local preference value of 100 is used. The

default value can be changed using the bgp default local-preference command.

4. If one of the paths is a redistributed path, which results from a redistribute or network command,

then it is chosen. Otherwise, if one of the paths is a locally generated aggregate, which results from

an aggregate-address command, it is chosen.

Note Steps 1 through 4 implement the “Degree of Preference” calculation from Section 9.1.1 of

draft-ietf-idr-bgp4-24.txt.

5. If the paths have unequal AS path lengths, the path with the shorter AS path is chosen. This step is

skipped if bgp bestpath as-path ignore command is configured. Note: when calculating the length

of the AS path, confederation segments are ignored, and AS sets count as 1. (See Section 9.1.2.2a

of draft-ietf-idr-bgp4-24.txt.)

6. If the paths have different origins, the path with the lower origin is selected. Interior Gateway

Protocol (IGP) is considered lower than EGP, which is considered lower than INCOMPLETE. (See

Section 9.1.2.2b of draft-ietf-idr-bgp4-24.txt.)

7. If appropriate, the MED of the paths is compared. If they are unequal, the path with the lower MED

is chosen.

A number of configuration options exist that affect whether or not this step is performed. In general,

the MED is compared if both paths were received from neighbors in the same AS; otherwise the

MED comparison is skipped. However, this behavior is modified by certain configuration options,

and there are also some corner cases to consider. (See Section 9.1.2.2c of draft-ietf-idr-bgp4-24.txt.)

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If the bgp bestpath med always command is configured, then the MED comparison is always

performed, regardless of neighbor AS in the paths. Otherwise, MED comparison depends on the AS

paths of the two paths being compared, as follows:

a. If a path has no AS path or the AS path starts with an AS_SET, then the path is considered to

be internal, and the MED is compared with other internal paths

b. If the AS path starts with an AS_SEQUENCE, then the neighbor AS is the first AS number in

the sequence, and the MED is compared with other paths that have the same neighbor AS

c. If the AS path contains only confederation segments or starts with confederation segments

followed by an AS_SET, then the MED is not compared with any other path unless the bgp

bestpath med confed command is configured. In that case, the path is considered internal and

the MED is compared with other internal paths.

d. If the AS path starts with confederation segments followed by an AS_SEQUENCE, then the

neighbor AS is the first AS number in the AS_SEQUENCE, and the MED is compared with

other paths that have the same neighbor AS.

Note: if no MED attribute was received with the path, then the MED is considered to be 0 unless the

bgp bestpath med missing-as-worst command is configured. In that case, if no MED attribute was

received, the MED is considered to be the highest possible value.

8. If one path is received from an external peer and the other is received from an internal (or

confederation) peer, the path from the external peer is chosen. (See Section 9.1.2.2d of

draft-ietf-idr-bgp4-24.txt.)

9. If the paths have different IGP metrics to their next hops, the path with the lower IGP metric is

chosen. (See Section 9.1.2.2e of draft-ietf-idr-bgp4-24.txt.)

10. If all path parameters in steps 1 through 10 are the same, then the router IDs are compared. If the

path was received with an originator attribute, then that is used as the router ID to compare;

otherwise, the router ID of the neighbor from which the path was received is used. If the paths have

different router IDs, the path with the lower router ID is chosen. Note: where the originator is used

as the router ID, it is possible to have two paths with the same router ID. It is also possible to have

two BGP sessions with the same peer router, and therefore receive two paths with the same router

ID. (See Section 9.1.2.2f of draft-ietf-idr-bgp4-24.txt.)

11. If the paths have different cluster lengths, the path with the shorter cluster length is selected. If a

path was not received with a cluster list attribute, it is considered to have a cluster length of 0.

12. Finally, the path received from the neighbor with the lower IP address is chosen. Locally generated

paths (for example, redistributed paths) are considered to have a neighbor IP address of 0. (See

Section 9.1.2.2g of draft-ietf-idr-bgp4-24.txt.)

Order of Comparisons

The second part of the BGP best path algorithm implementation determines the order in which the paths

should be compared. The order of comparison is determined as follows:

1. The paths are partitioned into groups such that within each group the MED can be compared among

all paths. The same rules as in the “Comparing Pairs of Paths” section on page RC-19 are used to

determine whether MED can be compared between any two paths. Normally, this comparison results

in one group for each neighbor AS. If the bgp bestpath med always command is configured, then

there is just one group containing all the paths.

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2. The best path in each group is determined. Determining the best path is achieved by iterating through

all paths in the group and keeping track of the best one seen so far. Each path is compared with the

best-so-far, and if it is better, it becomes the new best-so-far and is compared with the next path in

the group.

3. A set of paths is formed containing the best path selected from each group in step 2. The overall best

path is selected from this set of paths, by iterating through them as in step 2.

Best Path Change Suppression

The third part of the implementation is to determine whether the best path change can be suppressed or

not—whether the new best path should be used, or continue using the existing best path. The existing

best path can continue to be used if the new one is identical to the point at which the best path selection

algorithm becomes arbitrary (if the router-id is the same). Continuing to use the existing best path can

avoid churn in the network.

Note This suppression behavior does not comply with the IETF Networking Working Group

draft-ietf-idr-bgp4-24.txt document, but is specified in the IETF Networking Working Group

draft-ietf-idr-avoid-transition-00.txt document.

The suppression behavior can be turned off by configuring the bgp bestpath compare-routerid

command. If this command is configured, the new best path is always preferred to the existing one.

Otherwise, the following steps are used to determine whether the best path change can be suppressed:

1. If the existing best path is no longer valid, the change cannot be suppressed.

2. If either the existing or new best paths were received from internal (or confederation) peers or were

locally generated (for example, by redistribution), then the change cannot be suppressed. That is,

suppression is possible only if both paths were received from external peers.

3. If the paths were received from the same peer (the paths would have the same router-id), the change

cannot be suppressed. The router ID is calculated using rules in the “Comparing Pairs of Paths”

section on page RC-19.

4. If the paths have different weights, local preferences, origins, or IGP metrics to their next hops, then

the change cannot be suppressed. Note that all of these values are calculated using the rules in the

“Comparing Pairs of Paths” section on page RC-19.

5. If the paths have different-length AS paths and the bgp bestpath as-path ignore command is not

configured, then the change cannot be suppressed. Again, the AS path length is calculated using the

rules in the “Comparing Pairs of Paths” section on page RC-19.

6. If the MED of the paths can be compared and the MEDs are different, then the change cannot be

suppressed. The decision as to whether the MEDs can be compared is exactly the same as the rules

in the “Comparing Pairs of Paths” section on page RC-19, as is the calculation of the MED value.

7. If all path parameters in steps 1 through 6 do not apply, the change can be suppressed.

Multiprotocol BGP

Multiprotocol BGP is an enhanced BGP that carries routing information for multiple network layer

protocols and IP multicast routes. BGP carries two sets of routes, one set for unicast routing and one set

for multicast routing. The routes associated with multicast routing are used by the Protocol Independent

Multicast (PIM) feature to build data distribution trees.

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Multiprotocol BGP is useful when you want a link dedicated to multicast traffic, perhaps to limit which

resources are used for which traffic. Multiprotocol BGP allows you to have a unicast routing topology

different from a multicast routing topology providing more control over your network and resources.

In BGP, the only way to perform interdomain multicast routing was to use the BGP infrastructure that

was in place for unicast routing. Perhaps you want all multicast traffic exchanged at one network access

point (NAP). If those routers were not multicast capable, or there were differing policies for which you

wanted multicast traffic to flow, multicast routing could not be supported without multiprotocol BGP.

Note It is possible to configure BGP peers that exchange both unicast and multicast network layer reachability

information (NLRI), but you cannot connect multiprotocol BGP clouds with a BGP cloud. That is, you

cannot redistribute multiprotocol BGP routes into BGP.

Figure 1 illustrates simple unicast and multicast topologies that are incongruent, and therefore are not

possible without multiprotocol BGP.

Autonomous systems 100, 200, and 300 are each connected to two NAPs that are FDDI rings. One is

used for unicast peering (and therefore the exchange of unicast traffic). The Multicast Friendly

Interconnect (MFI) ring is used for multicast peering (and therefore the exchange of multicast traffic).

Each router is unicast and multicast capable.

Figure 1 Incongruent Unicast and Multicast Routes

Figure 2 is a topology of unicast-only routers and multicast-only routers. The two routers on the left are

unicast-only routers (that is, they do not support or are not configured to perform multicast routing). The

two routers on the right are multicast-only routers. Routers A and B support both unicast and multicast

routing. The unicast-only and multicast-only routers are connected to a single NAP.

In Figure 2, only unicast traffic can travel from Router A to the unicast routers to Router B and back.

Multicast traffic could not flow on that path, so another routing table is required. Multicast traffic uses

the path from Router A to the multicast routers to Router B and back.

Figure 2 illustrates a multiprotocol BGP environment with a separate unicast route and multicast route

from Router A to Router B. Multiprotocol BGP allows these routes to be incongruent. Both of the

autonomous systems must be configured for internal multiprotocol BGP (IMBGP) in the figure.

Unicast

AS 100 AS 200

ISP B

FDDI FDDI

ISP A ISP C

12238

AS 300

MFI

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A multicast routing protocol, such as PIM, uses the multicast BGP database to perform Reverse Path

Forwarding (RPF) lookups for multicast-capable sources. Thus, packets can be sent and accepted on the

multicast topology but not on the unicast topology.

Figure 2 Multicast BGP Environment

Route Dampening

Route dampening is a BGP feature that minimizes the propagation of flapping routes across an

internetwork. A route is considered to be flapping when it is repeatedly available, then unavailable, then

available, then unavailable, and so on.

For example, consider a network with three BGP autonomous systems: autonomous system 1,

autonomous system 2, and autonomous system 3. Suppose the route to network A in autonomous system

1 flaps (it becomes unavailable). Under circumstances without route dampening, the eBGP neighbor of

autonomous system 1 to autonomous system 2 sends a withdraw message to autonomous system 2. The

border router in autonomous system 2, in turn, propagates the withdrawal message to autonomous

system 3. When the route to network A reappears, autonomous system 1 sends an advertisement message

to autonomous system 2, which sends it to autonomous system 3. If the route to network A repeatedly

becomes unavailable, then available, many withdrawal and advertisement messages are sent. Route

flapping is a problem in an internetwork connected to the Internet because a route flap in the Internet

backbone usually involves many routes.

AS 200

IMBGP

NAP

IMBGP

Router A

Unicast

router

Unicast route Multicast route

Unicast

router

Multicast

router

Router B

Multicast

router

11754

AS 100

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Note No penalty is applied to a BGP peer reset when route dampening is enabled. Although the reset

withdraws the route, no penalty is applied in this instance, even if route flap dampening is enabled.

Minimizing Flapping

The route dampening feature minimizes the flapping problem as follows. Suppose again that the route

to network A flaps. The router in autonomous system 2 (in which route dampening is enabled) assigns

network A a penalty of 1000 and moves it to history state. The router in autonomous system 2 continues

to advertise the status of the route to neighbors. The penalties are cumulative. When the route flaps so

often that the penalty exceeds a configurable suppression limit, the router stops advertising the route to

network A, regardless of how many times it flaps. Thus, the route is dampened.

The penalty placed on network A is decayed until the reuse limit is reached, upon which the route is once

again advertised. At half of the reuse limit, the dampening information for the route to network A is

removed.

BGP Routing Domain Confederation

One way to reduce the iBGP mesh is to divide an autonomous system into multiple subautonomous

systems and group them into a single confederation. To the outside world, the confederation looks like

a single autonomous system. Each autonomous system is fully meshed within itself and has a few

connections to other autonomous systems in the same confederation. Although the peers in different

autonomous systems have eBGP sessions, they exchange routing information as if they were iBGP peers.

Specifically, the next hop, MED, and local preference information is preserved. This feature allows the

you to retain a single IGP for all of the autonomous systems.

BGP Route Reflectors

BGP requires that all iBGP speakers be fully meshed. However, this requirement does not scale well

when there are many iBGP speakers. Instead of configuring a confederation, another way to reduce the

iBGP mesh is to configure a route reflector.

Figure 3 illustrates a simple iBGP configuration with three iBGP speakers (routers A, B, and C). Without

route reflectors, when Router A receives a route from an external neighbor, it must advertise it to both

routers B and C. Routers B and C do not readvertise the iBGP learned route to other iBGP speakers

because the routers do not pass on routes learned from internal neighbors to other internal neighbors,

thus preventing a routing information loop.

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Figure 3 Three Fully Meshed iBGP Speakers

With route reflectors, all iBGP speakers need not be fully meshed because there is a method to pass

learned routes to neighbors. In this model, an iBGP peer is configured to be a route reflector responsible

for passing iBGP learned routes to a set of iBGP neighbors. In Figure 4, Router B is configured as a route

reflector. When the route reflector receives routes advertised from Router A, it advertises them to Router

C, and vice versa. This scheme eliminates the need for the iBGP session between routers A and C.

Figure 4 Simple BGP Model with a Route Reflector

The internal peers of the route reflector are divided into two groups: client peers and all other routers in

the autonomous system (nonclient peers). A route reflector reflects routes between these two groups.

The route reflector and its client peers form a cluster. The nonclient peers must be fully meshed with

each other, but the client peers need not be fully meshed. The clients in the cluster do not communicate

with iBGP speakers outside their cluster.

S4217

External

BGP

speaker

Routes

advertised

Fully meshed

autonomous

system

Routes

Routes not

advertised

Router A Router A

Router B

Router C

S4219

External

BGP

speaker

Partially meshed autonomous system

Route

reflector

Reflected

routes

Routes

Router A

Router B

Router A Router C

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Figure 5 More Complex BGP Route Reflector Model

Figure 5 illustrates a more complex route reflector scheme. Router A is the route reflector in a cluster

with routers B, C, and D. Routers E, F, and G are fully meshed, nonclient routers.

When the route reflector receives an advertised route, depending on the neighbor, it takes the following

actions:

•A route from an external BGP speaker is advertised to all clients and nonclient peers.

•A route from a nonclient peer is advertised to all clients.

•A route from a client is advertised to all clients and nonclient peers. Hence, the clients need not be

fully meshed.

Along with route reflector-aware BGP speakers, it is possible to have BGP speakers that do not

understand the concept of route reflectors. They can be members of either client or nonclient groups,

allowing an easy and gradual migration from the old BGP model to the route reflector model. Initially,

you could create a single cluster with a route reflector and a few clients. All other iBGP speakers could

be nonclient peers to the route reflector and then more clusters could be created gradually.

An autonomous system can have multiple route reflectors. A route reflector treats other route reflectors

just like other iBGP speakers. A route reflector can be configured to have other route reflectors in a client

group or nonclient group. In a simple configuration, the backbone could be divided into many clusters.

Each route reflector would be configured with other route reflectors as nonclient peers (thus, all route

reflectors are fully meshed). The clients are configured to maintain iBGP sessions with only the route

reflector in their cluster.

Usually, a cluster of clients has a single route reflector. In that case, the cluster is identified by the router

ID of the route reflector. To increase redundancy and avoid a single point of failure, a cluster might have

more than one route reflector. In this case, all route reflectors in the cluster must be configured with the

S4218

External

BGP

speaker

Routes

advertised

Route reflector

Cluster

Client Client Client

Nonclient

Partially meshed

autonomous system

Router A

Router B

Router G

Router F

Router E

Router C Router D

Router A

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cluster ID so that a route reflector can recognize updates from route reflectors in the same cluster. All

route reflectors serving a cluster should be fully meshed and all of them should have identical sets of

client and nonclient peers.

By default, the clients of a route reflector are not required to be fully meshed and the routes from a client

are reflected to other clients. However, if the clients are fully meshed, the route reflector need not reflect

routes to clients.

As the iBGP learned routes are reflected, routing information may loop. The route reflector model has

the following mechanisms to avoid routing loops:

•Originator ID is an optional, nontransitive BGP attribute. It is a 4-byte attributed created by a route

reflector. The attribute carries the router ID of the originator of the route in the local autonomous

system. Therefore, if a misconfiguration causes routing information to come back to the originator,

the information is ignored.

•Cluster-list is an optional, nontransitive BGP attribute. It is a sequence of cluster IDs that the route

has passed. When a route reflector reflects a route from its clients to nonclient peers, and vice versa,

it appends the local cluster ID to the cluster-list. If the cluster-list is empty, a new cluster-list is

created. Using this attribute, a route reflector can identify if routing information is looped back to

the same cluster due to misconfiguration. If the local cluster ID is found in the cluster-list, the

advertisement is ignored.

Default Address Family for show Commands

Most of the show commands require the address family (afi) and subsequent address family (safi) to be

specified as arguments. The Cisco IOS XR software parser provides the ability to set the afi and safi so

it is not necessary to specify them while executing a show command. The parser commands are:

•set default-afi {ipv4 | ipv6 | all}

•set default-safi {unicast | multicast | all}

The parser automatically sets the default afi value to ipv4 and default safi value to unicast. It is

necessary to use only the parser commands to change the default afi value from ipv4 or default safi value

from unicast. Any afi or safi keyword specified in a show command overrides the values set using the

parser commands. Use the following command to check the currently set value of the afi and safi:

•show default-afi-safi

How to Implement BGP on Cisco IOS XR Software

This section contains instructions for the following tasks:

•Enabling BGP Routing, page RC-28 (required)

•Configuring a Routing Domain Confederation for BGP, page RC-31 (optional)

•Resetting eBGP Session Immediately Upon Link Failure, page RC-33 (optional)

•Logging Neighbor Changes, page RC-34 (optional)

•Adjusting BGP Timers, page RC-34 (optional)

•Changing the BGP Default Local Preference Value, page RC-35 (optional)

•Configuring the MED Metric for BGP, page RC-36 (optional)

•Configuring BGP Weights, page RC-38 (optional)

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•Tuning the BGP Best Path Calculation, page RC-39 (optional)

•Indicating BGP Backdoor Routes, page RC-41 (optional)

•Configuring Aggregate Addresses, page RC-43 (optional)

•Redistributing iBGP Routes into IGP, page RC-44 (optional)

•Redistributing Prefixes into Multiprotocol BGP, page RC-46 (optional)

•Configuring BGP Route Dampening, page RC-48 (optional)

•Applying Policy When Updating the Routing Table, page RC-52 (optional)

•Setting BGP Administrative Distance, page RC-53 (optional)

•Configuring a BGP Neighbor Group, page RC-55 (optional)

•Configuring a BGP Neighbor, page RC-58 (required)

•Configuring a Route Reflector for BGP, page RC-60 (optional)

•Configuring BGP Route Filtering by Route Policy, page RC-62 (optional)

•Disabling Next Hop Processing on BGP Updates, page RC-64 (optional)

•Configuring BGP Community and Extended-Community Filtering, page RC-65 (optional)

•Configuring Software to Store Updates from a Neighbor, page RC-67 (optional)

•Disabling a BGP Neighbor, page RC-69 (optional)

•Resetting Neighbors Using BGP Dynamic Inbound Soft Reset, page RC-71 (optional)

•Resetting Neighbors Using BGP Outbound Soft Reset, page RC-71 (optional)

•Resetting Neighbors Using BGP Hard Reset, page RC-72 (optional)

•Clearing Caches, Tables and Databases, page RC-73 (optional)

•Displaying System and Network Statistics, page RC-73 (optional)

•Monitoring BGP Update Groups, page RC-75 (optional)

Enabling BGP Routing

Perform this task to enable BGP routing and establish a BGP routing process. Configuring BGP

neighbors is included as part of enabling BGP routing.

Note At least one neighbor and at least one address family must be configured to enable BGP routing. At least

one neighbor with both a remote AS and an address family must be configured globally using the

address family and remote as commands.

Prerequisites

BGP must be able to obtain a router identifier (for example, a configured loopback address). At least,

one address family must be configured in the BGP router configuration and the same address family must

also be configured under the neighbor.

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Restrictions

If the neighbor is configured as an external BGP (eBGP) peer, you must configure an inbound and

outbound route policy on the neighbor using the route-policy command.

SUMMARY STEPS

1. configure

2. route-policy name

3. end-policy

4. end

commit

5. configure

6. router bgp autonomous-system-number

7. bgp router-id {ip-address | interface-type interface-instance}

8. neighbor ip-address

9. remote-as autonomous-system-number

10. address-family {ipv4 unicast | ipv4 multicast | ipv6 unicast | ipv6 multicast}

11. route-policy route-policy-name {in | out}

12. end

commit

DETAILED STEPS

Command or Action Purpose

Step 1 configure

Example:

RP/0/RP0/CPU0:router# configure

Enters global configuration mode.

Step 2 route-policy

name

Example:

RP/0/RP0/CPU0:router(config)# route-policy

drop-as-1234

RP/0/RP0/CPU0:router(config-rpl)# if as-path

passes-through '1234' then

RP/0/RP0/CPU0:router(config-rpl)# apply

check-communities

RP/0/RP0/CPU0:router(config-rpl)# else

RP/0/RP0/CPU0:router(config-rpl)# pass

RP/0/RP0/CPU0:router(config-rpl)# endif

(Optional) Defines a route policy named drop-as-1234 and

enters route policy configuration mode.

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Step 3 end-policy

Example:

RP/0/RP0/CPU0:router(config-rpl)# end-policy

(Optional) Ends the definition of a route policy and exits

route policy configuration mode.

Step 4 end

commit

Example:

RP/0/RP0/CPU0:router(config)# end

RP/0/RP0/CPU0:router(config)# commit

Saves configuration changes.

•When you issue the end command, the system prompts

you to commit changes:

Uncommitted changes found, commit them before

exiting(yes/no/cancel)?

[cancel]:

–

Entering yes saves configuration changes to the

running configuration file, exits the configuration

session, and returns the router to EXEC mode.

–

Entering no exits the configuration session and

returns the router to EXEC mode without

committing the configuration changes.

–

Entering cancel leaves the router in the current

configuration session without exiting or

committing the configuration changes.

•Use the commit command to save the configuration

changes to the running configuration file and remain

within the configuration session.

Step 5 configure

Example:

RP/0/RP0/CPU0:router# configure

Enters global configuration mode.

Step 6 router bgp

autonomous-system-number

Example:

RP/0/RP0/CPU0:router(config)# router bgp 120

Enters BGP configuration mode allowing you to configure

the BGP routing process.

Step 7 bgp router-id {

ip-address

interface-type

interface-instance

}

Example:

RP/0/RP0/CPU0:router(config-bgp)# bgp router-id

192.168.70.24

Configures the local router with a router id of

192.168.70.24.

Step 8 neighbor

ip-address

Example:

RP/0/RP0/CPU0:router(config-bgp)# neighbor

172.168.40.24

Places the router in neighbor configuration mode for BGP

routing and configures the neighbor IP address

172.168.40.24 as a BGP peer.

Command or Action Purpose

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Configuring a Routing Domain Confederation for BGP

Perform this task to configure the routing domain confederation for BGP. This includes specifying a

confederation identifier and autonomous systems that belong to the confederation.

Configuring a routing domain confederation reduces the internal BGP (iBGP) mesh by dividing an

autonomous system into multiple autonomous systems and grouping them into a single confederation.

Each autonomous system is fully meshed within itself and has a few connections to another autonomous

system in the same confederation. The confederation maintains the next hop and local preference

information, and that allows you to retain a single Interior Gateway Protocol (IGP) for all autonomous

systems. To the outside world, the confederation looks like a single autonomous system.

Step 9 remote-as

autonomous-system-number

Example:

RP/0/RP0/CPU0:router(config-bgp-nbr)# remote-as

2002

Creates a neighbor and assigns it a remote autonomous

system number of 2002.

Step 10 address-family {ipv4 unicast | ipv4 multicast |

ipv6 unicast | ipv6 multicast}

Example:

RP/0/RP0/CPU0:router(config-bgp-nbr)#

address-family ipv4 unicast

Enters global address family configuration mode for the

IPv4 address family.

Step 11 route-policy

route-policy-name

{in | out}

Example:

RP/0/RP0/CPU0:router(config-bgp-nbr-af)#

route-policy In-Ipv4 in

(Optional) Applies the In-Ipv4 policy to inbound IPv4

unicast routes.

Step 12 end

commit

Example:

RP/0/RP0/CPU0:router(config-bgp-nbr-af)# end

RP/0/RP0/CPU0:router(config-bgp-nbr-af)# commit

Saves configuration changes.

•When you issue the end command, the system prompts

you to commit changes:

Uncommitted changes found, commit them before

exiting(yes/no/cancel)?

[cancel]:

–

Entering yes saves configuration changes to the

running configuration file, exits the configuration

session, and returns the router to EXEC mode.

–

Entering no exits the configuration session and

returns the router to EXEC mode without

committing the configuration changes.

–

Entering cancel leaves the router in the current

configuration session without exiting or

committing the configuration changes.

•Use the commit command to save the configuration

changes to the running configuration file and remain

within the configuration session.

Command or Action Purpose

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SUMMARY STEPS

1. configure

2. router bgp autonomous-system-number

3. bgp confederation identifier autonomous-system-number

4. bgp confederation peers autonomous-system-number

5. end

commit

DETAILED STEPS

Command or Action Purpose

Step 1 configure

Example:

RP/0/RP0/CPU0:router# configure

Enters global configuration mode.

Step 2 router bgp

autonomous-system-number

Example:

RP/0/RP0/CPU0:router(config)# router bgp 120

Enters BGP configuration mode allowing you to configure

the BGP routing process.

Step 3 bgp confederation identifier

autonomous-system-number

Example:

RP/0/RP0/CPU0:router(config-bgp)# bgp

confederation identifier 5

Specifies a BGP confederation identifier of 5.

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Resetting eBGP Session Immediately Upon Link Failure

Immediately resetting BGP sessions of any directly adjacent external peers if the link used to reach them

goes down is enabled by default. Use the bgp fast-external-fallover disable command to disable

automatic resetting. The bgp fast-external-fallover disable command can also be used to turn the

automatic reset back on.

Step 4 bgp confederation peers

autonomous-system-number

Example:

RP/0/RP0/CPU0:router(config-bgp)# bgp

confederation peers 1091

RP/0/RP0/CPU0:router(config-bgp)# bgp

confederation peers 1092

RP/0/RP0/CPU0:router(config-bgp)# bgp

confederation peers 1093

RP/0/RP0/CPU0:router(config-bgp)# bgp

confederation peers 1094

RP/0/RP0/CPU0:router(config-bgp)# bgp

confederation peers 1095

RP/0/RP0/CPU0:router(config-bgp)# bgp

confederation peers 1096

Specifies that the BGP autonomous systems 1091, 1092,

1093, 1094, 1095, and 1096 belong to BGP confederation

identifier 5.

Step 5 end

commit

Example:

RP/0/RP0/CPU0:router(config-bgp)# end

RP/0/RP0/CPU0:router(config-bgp)# commit

Saves configuration changes.

•When you issue the end command, the system prompts

you to commit changes:

Uncommitted changes found, commit them before

exiting(yes/no/cancel)?

[cancel]:

–

Entering yes saves configuration changes to the

running configuration file, exits the configuration

session, and returns the router to EXEC mode.

–

Entering no exits the configuration session and

returns the router to EXEC mode without

committing the configuration changes.

–

Entering cancel leaves the router in the current

configuration session without exiting or

committing the configuration changes.

•Use the commit command to save the configuration

changes to the running configuration file and remain

within the configuration session.

Command or Action Purpose

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Logging Neighbor Changes

Logging neighbor changes is enabled by default. Use the log neighbor changes disable command to

turn off logging. The log neighbor changes disable command can also be used to turn logging back on

if it has been disabled.

Adjusting BGP Timers

Perform this task to set the timers for BGP neighbors.

BGP uses certain timers to control periodic activities, such as the sending of keepalive messages and the

interval after which a neighbor is assumed to be down if no messages are received from the neighbor

during the interval. The values set using the timers bgp command can be overridden on particular

neighbors using the timers command in the neighbor configuration mode.

SUMMARY STEPS

1. configure

2. router bgp autonomous-system-number

3. timers bgp keepalive hold-time

4. neighbor ip-address

5. timers keepalive hold-time

6. end

commit

DETAILED STEPS

Command or Action Purpose

Step 1 configure

Example:

RP/0/RP0/CPU0:router# configure

Enters global configuration mode.

Step 2 router bgp

autonomous-system-number

Example:

RP/0/RP0/CPU0:router(config)# router bgp 120

Enters BGP configuration mode allowing you to configure

the BGP routing process.

Step 3 timers bgp

keepalive hold-time

Example:

RP/0/RP0/CPU0:router(config-bgp)# timers bgp 30

Sets a default keepalive time of 30 seconds and a default

hold time of 90 seconds for all neighbors.

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Changing the BGP Default Local Preference Value

Perform this task to set the default local preference value for BGP paths.

SUMMARY STEPS

1. configure

2. router bgp autonomous-system-number

3. bgp default local-preference value

4. end

commit

Step 4 neighbor

ip-address

Example:

RP/0/RP0/CPU0:router(config-bgp)# neighbor

172.168.40.24

Places the router in neighbor configuration mode for BGP

routing and configures the neighbor IP address

172.168.40.24 as a BGP peer.

Step 5 timers

keepalive hold-time

Example:

RP/0/RP0/CPU0:router(config-bgp-nbr)# timers 60

220

(Optional) Sets the keepalive timer to 60 seconds and the

hold-time timer to 220 seconds for BGP neighbor

172.168.40.24.

Step 6 end

commit

Example:

RP/0/RP0/CPU0:router(config-bgp-nbr)# end

RP/0/RP0/CPU0:router(config-bgp-nbr)# commit

Saves configuration changes.

•When you issue the end command, the system prompts

you to commit changes:

Uncommitted changes found, commit them before

exiting(yes/no/cancel)?

[cancel]:

–

Entering yes saves configuration changes to the

running configuration file, exits the configuration

session, and returns the router to EXEC mode.

–

Entering no exits the configuration session and

returns the router to EXEC mode without

committing the configuration changes.

–

Entering cancel leaves the router in the current

configuration session without exiting or

committing the configuration changes.

•Use the commit command to save the configuration

changes to the running configuration file and remain

within the configuration session.

Command or Action Purpose

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DETAILED STEPS

Configuring the MED Metric for BGP

Perform this task to set the multi exit discriminator (MED) to advertise to peers for routes that do not

already have a metric set (routes that were received with no MED attribute).

SUMMARY STEPS

1. configure

2. router bgp autonomous-system-number

3. default-metric value

Command or Action Purpose

Step 1 configure

Example:

RP/0/RP0/CPU0:router# configure

Enters global configuration mode.

Step 2 router bgp

autonomous-system-number

Example:

RP/0/RP0/CPU0:router(config)# router bgp 120

Enters BGP configuration mode allowing you to configure

the BGP routing process.

Step 3 bgp default local-preference

value

Example:

RP/0/RP0/CPU0:router(config-bgp)# bgp default

local-preference 200

Sets the default local preference value from the default of

100 to 200, making it a more preferable path.

Step 4 end

commit

Example:

RP/0/RP0/CPU0:router(config-bgp)# end

RP/0/RP0/CPU0:router(config-bgp)# commit

Saves configuration changes.

•When you issue the end command, the system prompts

you to commit changes:

Uncommitted changes found, commit them before

exiting(yes/no/cancel)?

[cancel]:

–

Entering yes saves configuration changes to the

running configuration file, exits the configuration

session, and returns the router to EXEC mode.

–

Entering no exits the configuration session and

returns the router to EXEC mode without

committing the configuration changes.

–

Entering cancel leaves the router in the current

configuration session without exiting or

committing the configuration changes.

•Use the commit command to save the configuration

changes to the running configuration file and remain

within the configuration session.

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4. end

commit

DETAILED STEPS

Command or Action Purpose

Step 1 configure

Example:

RP/0/RP0/CPU0:router# configure

Enters global configuration mode.

Step 2 router bgp

autonomous-system-number

Example:

RP/0/RP0/CPU0:router(config)# router bgp 120

Enters BGP configuration mode allowing you to configure

the BGP routing process.

Step 3 default-metric

value

Example:

RP/0/RP0/CPU0:router(config-bgp)# default

metric 10

Sets the default metric to 10, which is used to set the MED

to advertise to peers for routes that do not already have a

metric set (routes that were received with no MED

attribute).

Step 4 end

commit

Example:

RP/0/RP0/CPU0:router(config-bgp)# end

RP/0/RP0/CPU0:router(config-bgp)# commit

Saves configuration changes.

•When you issue the end command, the system prompts

you to commit changes:

Uncommitted changes found, commit them before

exiting(yes/no/cancel)?

[cancel]:

–

Entering yes saves configuration changes to the

running configuration file, exits the configuration

session, and returns the router to EXEC mode.

–

Entering no exits the configuration session and

returns the router to EXEC mode without

committing the configuration changes.

–

Entering cancel leaves the router in the current

configuration session without exiting or

committing the configuration changes.

•Use the commit command to save the configuration

changes to the running configuration file and remain

within the configuration session.

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Configuring BGP Weights

Perform this task to assign a weight to routes received from a neighbor. A weight is a number that you

can assign to a path so that you can control the best path selection process. If you have particular

neighbors that you want to prefer for most of your traffic, you can use the weight command to assign a

higher weight to all routes learned from that neighbor.

Restrictions

The clear bgp command must be used for the newly configured weight to take effect.

SUMMARY STEPS

1. configure

2. router bgp autonomous-system-number

3. neighbor ip-address

4. remote-as autonomous-system-number

5. address-family {ipv4 unicast | ipv4 multicast | ipv6 unicast | ipv6 multicast}

6. weight weight-value

7. end

commit

DETAILED STEPS

Command or Action Purpose

Step 1 configure

Example:

RP/0/RP0/CPU0:router# configure

Enters global configuration mode.

Step 2 router bgp

autonomous-system-number

Example:

RP/0/RP0/CPU0:router(config)# router bgp 120

Enters BGP configuration mode allowing you to configure

the BGP routing process.

Step 3 neighbor

ip-address

Example:

RP/0/RP0/CPU0:router(config-bgp)# neighbor

172.168.40.24

Places the router in neighbor configuration mode for BGP

routing and configures the neighbor IP address

172.168.40.24 as a BGP peer.

Step 4 remote-as

autonomous-system-number

Example:

RP/0/RP0/CPU0:router(config-bgp-nbr)# remote-as

2002

Creates a neighbor and assigns it a remote autonomous

system number of 2002.

Implementing BGP on Cisco IOS XR Software

How to Implement BGP on Cisco IOS XR Software

RC-39

Cisco IOS XR Routing Configuration Guide

Tuning the BGP Best Path Calculation

Perform this task to change the default BGP best path calculation behavior.

SUMMARY STEPS

1. configure

2. router bgp autonomous-system-number

3. bgp bestpath med missing-as-worst

4. bgp bestpath med always

5. bgp bestpath med confed

6. bgp bestpath as-path ignore

7. bgp bestpath compare-routerid

Step 5 address-family {ipv4 unicast | ipv4 multicast |

ipv6 unicast | ipv6 multicast}

Example:

RP/0/RP0/CPU0:router(config-bgp-nbr)#

address-family ipv4 unicast

Enters neighbor address family configuration mode for the

IPv4 address family.

Step 6 weight

weight-value

Example:

RP/0/RP0/CPU0:router(config-bgp-nbr-af)# weight

41150

Assigns a weight of 41150 to all IPv4 unicast routes learned

through 172.168.40.24.

Step 7 end

commit

Example:

RP/0/RP0/CPU0:router(config-bgp-nbr-af)# end

RP/0/RP0/CPU0:router(config-bgp-nbr-af)# commit

Saves configuration changes.

•When you issue the end command, the system prompts

you to commit changes:

Uncommitted changes found, commit them before

exiting(yes/no/cancel)?

[cancel]:

–

Entering yes saves configuration changes to the

running configuration file, exits the configuration

session, and returns the router to EXEC mode.

–

Entering no exits the configuration session and

returns the router to EXEC mode without

committing the configuration changes.

–

Entering cancel leaves the router in the current

configuration session without exiting or

committing the configuration changes.

•Use the commit command to save the configuration

changes to the running configuration file and remain

within the configuration session.

Command or Action Purpose

Implementing BGP on Cisco IOS XR Software

How to Implement BGP on Cisco IOS XR Software

RC-40

Cisco IOS XR Routing Configuration Guide

8. end

commit

DETAILED STEPS

Command or Action Purpose

Step 1 configure

Example:

RP/0/RP0/CPU0:router# configure

Enters global configuration mode.

Step 2 router bgp

autonomous-system-number

Example:

RP/0/RP0/CPU0:router(config)# router bgp 120

Enters BGP configuration mode allowing you to configure

the BGP routing process.

Step 3 bgp bestpath med missing-as-worst

Example:

RP/0/RP0/CPU0:router(config-bgp)# bgp bestpath

med missing-as-worst

Directs the BGP software to consider a missing MED

attribute in a path as having a value of infinity, making this

path the least desirable path.

Step 4 bgp bestpath med always

Example:

RP/0/RP0/CPU0:router(config-bgp)# bgp bestpath

med always

Configures the BGP speaker in autonomous system 120 to

compare MEDs among alternative paths, regardless of the

autonomous system from which the paths are received.

Step 5 bgp bestpath med confed

Example:

RP/0/RP0/CPU0:router(config-bgp)# bgp bestpath

med confed

Enables BGP software to compare MED values for paths

learned from confederation peers.

Step 6 bgp bestpath as-path ignore

Example:

RP/0/RP0/CPU0:router(config-bgp)# bgp bestpath

as-path ignore

Configures the BGP software to ignore the autonomous

system length when performing best path selection.

Implementing BGP on Cisco IOS XR Software

How to Implement BGP on Cisco IOS XR Software

RC-41

Cisco IOS XR Routing Configuration Guide

Indicating BGP Backdoor Routes

Perform this task to set the administrative distance on an external Border Gateway Protocol (eBGP) route

to that of a locally sourced BGP route, causing it to be less preferred than an Interior Gateway Protocol

(IGP) route.

SUMMARY STEPS

1. configure

2. router bgp autonomous-system-number

3. address-family {ipv4 unicast | ipv4 multicast | ipv6 unicast | ipv6 multicast}

4. network {ip-address /prefix-length | ip-address mask} backdoor

5. end

commit

Step 7 bgp bestpath compare-routerid

Example:

RP/0/RP0/CPU0:router(config-bgp)# bgp bestpath

compare-routerid

Configure the BGP speaker in autonomous system 120 to

compare the router IDs of similar paths.

Step 8 end

commit

Example:

RP/0/RP0/CPU0:router(config-bgp)# end

RP/0/RP0/CPU0:router(config-bgp)# commit

Saves configuration changes.

•When you issue the end command, the system prompts

you to commit changes:

Uncommitted changes found, commit them before

exiting(yes/no/cancel)?

[cancel]:

–

Entering yes saves configuration changes to the

running configuration file, exits the configuration

session, and returns the router to EXEC mode.

–

Entering no exits the configuration session and

returns the router to EXEC mode without

committing the configuration changes.

–

Entering cancel leaves the router in the current

configuration session without exiting or

committing the configuration changes.

•Use the commit command to save the configuration

changes to the running configuration file and remain

within the configuration session.

Command or Action Purpose

Implementing BGP on Cisco IOS XR Software

How to Implement BGP on Cisco IOS XR Software

RC-42

Cisco IOS XR Routing Configuration Guide

DETAILED STEPS

Command or Action Purpose

Step 1 configure

Example:

RP/0/RP0/CPU0:router# configure

Enters global configuration mode.

Step 2 router bgp

autonomous-system-number

Example:

RP/0/RP0/CPU0:router(config)# router bgp 120

Enters BGP configuration mode allowing you to configure

the BGP routing process.

Step 3 address-family {ipv4 unicast | ipv4 multicast |

ipv6 unicast | ipv6 multicast}

Example:

RP/0/RP0/CPU0:router(config-bgp)#

address-family ipv4 unicast

Enters global address family configuration mode for the

IPv4 address family.

Step 4 network {

ip-address /prefix-length

ip-address

mask

} backdoor

Example:

RP/0/RP0/CPU0:router(config-bgp-af)# network

172.20.0.0/16

Configures the local router to originate and advertise the

IPv4 unicast network 172.20.0.0/16.

Step 5 end

commit

Example:

RP/0/RP0/CPU0:router(config-bgp-af)# end

RP/0/RP0/CPU0:router(config-bgp-af)# commit

Saves configuration changes.

•When you issue the end command, the system prompts

you to commit changes:

Uncommitted changes found, commit them before

exiting(yes/no/cancel)?

[cancel]:

–

Entering yes saves configuration changes to the

running configuration file, exits the configuration

session, and returns the router to EXEC mode.

–

Entering no exits the configuration session and

returns the router to EXEC mode without

committing the configuration changes.

–

Entering cancel leaves the router in the current

configuration session without exiting or

committing the configuration changes.

•Use the commit command to save the configuration

changes to the running configuration file and remain

within the configuration session.

Implementing BGP on Cisco IOS XR Software

How to Implement BGP on Cisco IOS XR Software

RC-43

Cisco IOS XR Routing Configuration Guide

Configuring Aggregate Addresses

Perform this task to create aggregate entries in a BGP routing table.

SUMMARY STEPS

1. configure

2. router bgp autonomous-system-number

3. address-family {ipv4 unicast | ipv4 multicast | ipv6 unicast | ipv6 multicast}

4. aggregate-address address/mask-length [as-set] [as-confed-set] [summary-only] [route-policy

route-policy-name]

5. end

commit

DETAILED STEPS

Command or Action Purpose

Step 1 configure

Example:

RP/0/RP0/CPU0:router# configure

Enters global configuration mode.

Step 2 router bgp

autonomous-system-number

Example:

RP/0/RP0/CPU0:router(config)# router bgp 120

Enters BGP configuration mode allowing you to configure

the BGP routing process.

Step 3 address-family {ipv4 unicast | ipv4 multicast |

ipv6 unicast | ipv6 multicast}

Example:

RP/0/RP0/CPU0:router(config-bgp)#

address-family ipv4 unicast

Enters global address family configuration mode for the

IPv4 address family.

Implementing BGP on Cisco IOS XR Software

How to Implement BGP on Cisco IOS XR Software

RC-44

Cisco IOS XR Routing Configuration Guide

Redistributing iBGP Routes into IGP

Perform this task to redistribute iBGP routes into an Interior Gateway Protocol (IGP), such as

Intermediate System-to-Intermediate System (IS-IS) or Open Shortest Path First (OSPF).

Note Use of the bgp redistribute-internal command requires the clear route * command to be issued to

reinstall all BGP routes into the IP routing table.

Caution Redistributing iBGP routes into IGPs may cause routing loops to form within an autonomous system.

Use this command with caution.

Step 4 aggregate-address

address/mask-length

[as-set]

[as-confed-set] [summary-only] [route-policy

route-policy-name

]

Example:

RP/0/RP0/CPU0:router(config-bgp-af)#

aggregate-address 10.0.0.0/8 as-set

Creates an aggregate address. The path advertised for this

route is an autonomous system set consisting of all elements

contained in all paths that are being summarized.

•The as-set keyword generates autonomous system set

path information and community information from

contributing paths.

•The as-confed-set keyword generates autonomous

system confederation set path information from

contributing paths.

•The summary-only keyword filters all more specific

routes from updates.

•The route-policy route-policy-name keyword and

argument specify the route policy used to set the

attributes of the aggregate route.

Step 5 end

commit

Example:

RP/0/RP0/CPU0:router(config-bgp-af)# end

RP/0/RP0/CPU0:router(config-bgp-af)# commit

Saves configuration changes.

•When you issue the end command, the system prompts

you to commit changes:

Uncommitted changes found, commit them before

exiting(yes/no/cancel)?

[cancel]:

–

Entering yes saves configuration changes to the

running configuration file, exits the configuration

session, and returns the router to EXEC mode.

–

Entering no exits the configuration session and

returns the router to EXEC mode without

committing the configuration changes.

–

Entering cancel leaves the router in the current

configuration session without exiting or

committing the configuration changes.

•Use the commit command to save the configuration

changes to the running configuration file and remain

within the configuration session.

Command or Action Purpose

Implementing BGP on Cisco IOS XR Software

How to Implement BGP on Cisco IOS XR Software

RC-45

Cisco IOS XR Routing Configuration Guide

SUMMARY STEPS

1. configure

2. router bgp autonomous-system-number

3. bgp redistribute-internal

4. end

commit

DETAILED STEPS

Command or Action Purpose

Step 1 configure

Example:

RP/0/RP0/CPU0:router# configure

Enters global configuration mode.

Step 2 router bgp

autonomous-system-number

Example:

RP/0/RP0/CPU0:router(config)# router bgp 120

Enters BGP configuration mode allowing you to configure

the BGP routing process.

Step 3 bgp redistribute-internal

Example:

RP/0/RP0/CPU0:router(config-bgp)# bgp

redistribute-internal

Allows the redistribution of iBGP routes into an IGP, such

as IS-IS or OSPF.

Step 4 end

commit

Example:

RP/0/RP0/CPU0:router(config-bgp)# end

RP/0/RP0/CPU0:router(config-bgp)# commit

Saves configuration changes.

•When you issue the end command, the system prompts

you to commit changes:

Uncommitted changes found, commit them before

exiting(yes/no/cancel)?

[cancel]:

–

Entering yes saves configuration changes to the

running configuration file, exits the configuration

session, and returns the router to EXEC mode.

–

Entering no exits the configuration session and

returns the router to EXEC mode without

committing the configuration changes.

–

Entering cancel leaves the router in the current

configuration session without exiting or

committing the configuration changes.

•Use the commit command to save the configuration

changes to the running configuration file and remain

within the configuration session.

Implementing BGP on Cisco IOS XR Software

How to Implement BGP on Cisco IOS XR Software

RC-46

Cisco IOS XR Routing Configuration Guide

Redistributing Prefixes into Multiprotocol BGP

Perform this task to redistribute prefixes from another protocol into multiprotocol BGP.

Redistribution is the process of injecting prefixes from one routing protocol into another routing

protocol. This task shows how to inject prefixes from another routing protocol into multiprotocol BGP.

Specifically, prefixes that are redistributed into multiprotocol BGP using the redistribute command are

injected into the unicast database, the multicast database, or both.

SUMMARY STEPS

1. configure

2. router bgp autonomous-system-number

3. address-family {ipv4 unicast | ipv4 multicast | ipv6 unicast | ipv6 multicast}

4. redistribute connected [metric metric-value] [route-policy route-policy-name]

redistribute isis process-id [level {1 | 1-inter-area | 2}] [metric metric-value] [route-policy

route-policy-name]

redistribute ospf process-id [match {external [1 | 2] | internal | nssa-external [1 | 2]]} [metric

metric-value] [route-policy route-policy-name]

redistribute ospfv3 process-id [match {external [1 | 2] | internal | nssa-external [1 | 2]]} [metric

metric-value] [route-policy route-policy-name]

redistribute static [metric metric-value] [route-policy route-policy-name]

5. end

commit

DETAILED STEPS

Command or Action Purpose

Step 1 configure

Example:

RP/0/RP0/CPU0:router# configure

Enters global configuration mode.

Step 2 router bgp

autonomous-system-number

Example:

RP/0/RP0/CPU0:router(config)# router bgp 120

Enters BGP configuration mode allowing you to configure

the BGP routing process.

Step 3 address-family {ipv4 unicast | ipv4 multicast |

ipv6 unicast | ipv6 multicast}

Example:

RP/0/RP0/CPU0:router(config-bgp)#

address-family ipv4 unicast

Enters global address family configuration mode for the

IPv4 address family.

Implementing BGP on Cisco IOS XR Software

How to Implement BGP on Cisco IOS XR Software

RC-47

Cisco IOS XR Routing Configuration Guide

Step 4 redistribute connected [metric

metric-value

]

[route-policy

route-policy-name

]

redistribute isis

process-id

[level {1 |

1-inter-area | 2}] [metric

metric-value

]

[route-policy

route-policy-name

]

redistribute ospf

process-id

[match {external

[1 | 2] | internal | nssa-external [1 | 2]]}

[metric

metric-value

] [route-policy

route-policy-name

]

redistribute ospfv3

process-id

[match {external

[1 | 2] | internal | nssa-external [1 | 2]]}

[metric

metric-value

] [route-policy

route-policy-name

]

redistribute static [metric

metric-value

]

[route-policy

route-policy-name

]

Example:

RP/0/RP0/CPU0:router(config-bgp-af)#

redistribute ospf 110

Causes IPv4 unicast OSPF routes from OSPF instance 110

to be redistributed into BGP.

Step 5 end

commit

Example:

RP/0/RP0/CPU0:router(config-bgp-af)# end

RP/0/RP0/CPU0:router(config-bgp-af)# commit

Saves configuration changes.

•When you issue the end command, the system prompts

you to commit changes:

Uncommitted changes found, commit them before

exiting(yes/no/cancel)?

[cancel]:

–

Entering yes saves configuration changes to the

running configuration file, exits the configuration

session, and returns the router to EXEC mode.

–

Entering no exits the configuration session and

returns the router to EXEC mode without

committing the configuration changes.

–

Entering cancel leaves the router in the current

configuration session without exiting or

committing the configuration changes.

•Use the commit command to save the configuration

changes to the running configuration file and remain

within the configuration session.

Command or Action Purpose

Implementing BGP on Cisco IOS XR Software

How to Implement BGP on Cisco IOS XR Software

RC-48

Cisco IOS XR Routing Configuration Guide

Configuring BGP Route Dampening

Perform this task to configure and monitor BGP route dampening.

SUMMARY STEPS

1. configure

2. router bgp autonomous-system-number

3. address-family {ipv4 unicast | ipv4 multicast | ipv6 unicast | ipv6 multicast}

4. bgp dampening [half-life [reuse suppress max-suppress-time] | route-policy route-policy-name]

5. end

commit

6. show bgp [ipv4 {unicast | multicast | all} | ipv6 {unicast | all} | all {unicast | multicast | all}]

flap-statistics

7. show bgp [ipv4 {unicast | multicast | all} | ipv6 {unicast | all} | all {unicast | multicast | all}]

flap-statistics regexp regular-expression

8. show bgp [ipv4 {unicast | multicast | all} | ipv6 {unicast | all} | all {unicast | multicast | all}]

flap-statistics route-policy route-policy-name

9. show bgp [ipv4 {unicast | multicast | all} | ipv6 {unicast | all} | all {unicast | multicast | all}]

flap-statistics {ip-address [{mask | /prefix-length}

10. show bgp [ipv4 {unicast | multicast | all} | ipv6 {unicast | all} | all {unicast | multicast | all}]

flap-statistics {ip-address [{mask | /prefix-length} [longer-prefixes]]

11. clear bgp {ipv4 {unicast | multicast | all} | ipv6 {unicast | all} | all {unicast | multicast | all}}

flap-statistics

12. clear bgp {ipv4 {unicast | multicast | all} | ipv6 {unicast | all} | all {unicast | multicast | all}}

flap-statistics regexp regular-expression

13. clear bgp {ipv4 {unicast | multicast | all} | ipv6 {unicast | all} | all {unicast | multicast | all}}

flap-statistics route-policy route-policy-name

14. clear bgp {ipv4 {unicast | multicast | all} | ipv6 {unicast | all} | all {unicast | multicast | all}}

flap-statistics network/mask-length

15. clear bgp {ipv4 {unicast | multicast | all} | ipv6 {unicast | all} | all {unicast | multicast | all}}

flap-statistics ip-address

16. show bgp [ipv4 {unicast | multicast | all} | ipv6 {unicast | all} | all {unicast | multicast | all}]

dampened-paths

17. clear bgp {ipv4 {unicast | multicast | all} | ipv6 {unicast | all} | all {unicast | multicast | all}}

dampening [ip-address/mask-length]

Implementing BGP on Cisco IOS XR Software

How to Implement BGP on Cisco IOS XR Software

RC-49

Cisco IOS XR Routing Configuration Guide

DETAILED STEPS

Command or Action Purpose

Step 1 configure

Example:

RP/0/RP0/CPU0:router# configure

Enters global configuration mode.

Step 2 router bgp

autonomous-system-number

Example:

RP/0/RP0/CPU0:router(config)# router bgp 120

Enters BGP configuration mode allowing you to configure

the BGP routing process.

Step 3 address-family {ipv4 unicast | ipv4 multicast |

ipv6 unicast | ipv6 multicast}

Example:

RP/0/RP0/CPU0:router(config-bgp)#

address-family ipv4 unicast

Enters global address family configuration mode for the

IPv4 address family.

Step 4 bgp dampening [

half-life

[

reuse suppress

max-suppress-time

] | route-policy

route-policy-name

]

Example:

RP/0/RP0/CPU0:router(config-bgp-af)# bgp

dampening 30 1500 10000 120

Configures BGP dampening for the IPv4 address family.

The half-life argument is set to 30, the reuse argument is set

to 1500, the suppress argument is set to 10000, and the

max-suppress-time argument is set to 120.

Step 5 end

commit

Example:

RP/0/RP0/CPU0:router(config-bgp-af)# end

RP/0/RP0/CPU0:router(config-bgp-af)# commit

Saves configuration changes.

•When you issue the end command, the system prompts

you to commit changes:

Uncommitted changes found, commit them before

exiting(yes/no/cancel)?

[cancel]:

–

Entering yes saves configuration changes to the

running configuration file, exits the configuration

session, and returns the router to EXEC mode.

–

Entering no exits the configuration session and

returns the router to EXEC mode without

committing the configuration changes.

–

Entering cancel leaves the router in the current

configuration session without exiting or

committing the configuration changes.

•Use the commit command to save the configuration

changes to the running configuration file and remain

within the configuration session.

Implementing BGP on Cisco IOS XR Software

How to Implement BGP on Cisco IOS XR Software

RC-50

Cisco IOS XR Routing Configuration Guide

Step 6 show bgp [ipv4 {unicast | multicast | all} |

ipv6 {unicast | all} | all {unicast | multicast

| all}] flap-statistics

Example:

RP/0/RP0/CPU0:router# show bgp flap statistics

Displays BGP flap statistics for all paths.

Step 7 show bgp [ipv4 {unicast | multicast | all} |

ipv6 {unicast | all} | all {unicast | multicast

| all}] flap-statistics regexp

regular-expression

Example:

RP/0/RP0/CPU0:router# show bgp flap-statistics

regexp _1$

Displays BGP flap statistics for all paths that match the

regular expression _1$.

Step 8 show bgp [ipv4 {unicast | multicast | all} |

ipv6 {unicast | all} | all {unicast | multicast

| all}] flap-statistics route-policy

route-policy-name

Example:

RP/0/RP0/CPU0:router(config)# show bgp

flap-statistics route-policy policy_A

Displays BGP flap statistics for route policy policy_A.

Step 9 show bgp [ipv4 {unicast | multicast | all} |

ipv6 {unicast | all} | all {unicast | multicast

| all}] flap-statistics {

ip-address

[{

mask

/prefix-length

}

Example:

RP/0/RP0/CPU0:router# show bgp flap-statistics

172.20.1.1

Displays BGP flap statistics for neighbor 172.20.1.1.

Step 10 show bgp [ipv4 {unicast | multicast | all} |

ipv6 {unicast | all} | all {unicast | multicast

| all}] flap-statistics {

ip-address

[{

mask

/prefix-length

} [longer-prefixes]

Example:

RP/0/RP0/CPU0:router# show bgp flap-statistics

172.20.1.1 longer-prefixes

Displays BGP flap statistics for more specific entries for

neighbor 172.20.1.1.

Step 11 clear bgp {ipv4 {unicast | multicast | all} |

ipv6 {unicast | all} | all {unicast | multicast

| all}} flap-statistics

Example:

RP/0/RP0/CPU0:router# clear bgp all all

flap-statistics

Clears BGP flap statistics for all routes.

Command or Action Purpose

Implementing BGP on Cisco IOS XR Software

How to Implement BGP on Cisco IOS XR Software

RC-51

Cisco IOS XR Routing Configuration Guide

Step 12 clear bgp {ipv4 {unicast | multicast | all} |

ipv6 {unicast | all} | all {unicast | multicast

| all}} flap-statistics regexp

regular-expression

Example:

RP/0/RP0/CPU0:router# clear bgp ipv4 unicast

flap-statistics _1$

Clears BGP flap statistics for all paths that match the

regular expression _1$.

Step 13 clear bgp {ipv4 {unicast | multicast | all} |

ipv6 {unicast | all} | all {unicast | multicast

| all}} flap-statistics route-policy

route-policy-nane

Example:

RP/0/RP0/CPU0:router# clear bgp ipv4 unicast

flap-statistics route-policy policy_A

Clears BGP flap statistics for route policy policy_A.

Step 14 clear bgp {ipv4 {unicast | multicast | all} |

ipv6 {unicast | all} | all {unicast | multicast

| all}} flap-statistics

network/mask-length

Example:

RP/0/RP0/CPU0:router# clear bgp ipv4 unicast

flap-statistics 192.168.40.0/24

Clears BGP flap statistics for network 192.168.40.0/24.

Step 15 clear bgp {ipv4 {unicast | multicast | all} |

ipv6 {unicast | all} | all {unicast | multicast

| all}} flap-statistics

ip-address

Example:

RP/0/RP0/CPU0:router# clear bgp ipv4 unicast

flap-statistics 172.20.1.1

Clears BGP flap statistics for routes received from this

neighbor 172.20.1.1.

Step 16 show bgp [ipv4 {unicast | multicast | all} |

ipv6 {unicast | all} | all {unicast | multicast

| all}] dampened-paths

Example:

RP/0/RP0/CPU0:router# show bgp dampened paths

Displays the dampened routes, including the time

remaining before they are unsuppressed.

Step 17 clear bgp {ipv4 {unicast | multicast | all} |

ipv6 {unicast | all} | all {unicast | multicast

| all}} dampening [

ip-address/mask-length

]

Example:

RP/0/RP0/CPU0:router# clear bgp dampening

Clears route dampening information and unsuppresses the

suppressed routes.

Command or Action Purpose

Implementing BGP on Cisco IOS XR Software

How to Implement BGP on Cisco IOS XR Software

RC-52

Cisco IOS XR Routing Configuration Guide

Applying Policy When Updating the Routing Table

Perform this task to apply a routing policy to routes being installed into the routing table.

Prerequisites

See the Implementing Routing Policy on Cisco IOS XR Software module of the Cisco IOS XR Routing

Configuration Guide for a list of the supported attributes and operations that are valid for table policy

filtering.

SUMMARY STEPS

1. configure

2. router bgp autonomous-system-number

3. address-family {ipv4 unicast | ipv4 multicast | ipv6 unicast | ipv6 multicast}

4. table-policy policy-name

5. end

commit

DETAILED STEPS

Command or Action Purpose

Step 1 configure

Example:

RP/0/RP0/CPU0:router# configure

Enters global configuration mode.

Step 2 router bgp

autonomous-system-number

Example:

RP/0/RP0/CPU0:router(config)# router bgp 120

Enters BGP configuration mode allowing you to configure

the BGP routing process.

Step 3 address-family {ipv4 unicast | ipv4 multicast |

ipv6 unicast | ipv6 multicast}

Example:

RP/0/RP0/CPU0:router(config-bgp)#

address-family ipv4 unicast

Enters global address family configuration mode for the

IPv4 address family.

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Cisco IOS XR Routing Configuration Guide

Setting BGP Administrative Distance

Perform this task to specify the use of administrative distances that can be used to prefer one class of

route over another.

SUMMARY STEPS

1. configure

2. router bgp autonomous-system-number

3. address-family {ipv4 unicast | ipv4 multicast | ipv6 unicast | ipv6 multicast}

4. distance bgp external-distance internal-distance local-distance

5. end

commit

Step 4 table-policy

policy-name

Example:

RP/0/RP0/CPU0:router(config-bgp-af)#

table-policy tbl-plcy-A

Applies the tbl-plcy-A policy to IPv4 unicast routes being

installed into the routing table.

Step 5 end

commit

Example:

RP/0/RP0/CPU0:router(config-bgp-af)# end

RP/0/RP0/CPU0:router(config-bgp-af)# commit

Saves configuration changes.

•When you issue the end command, the system prompts

you to commit changes:

Uncommitted changes found, commit them before

exiting(yes/no/cancel)?

[cancel]:

–

Entering yes saves configuration changes to the

running configuration file, exits the configuration

session, and returns the router to EXEC mode.

–

Entering no exits the configuration session and

returns the router to EXEC mode without

committing the configuration changes.

–

Entering cancel leaves the router in the current

configuration session without exiting or

committing the configuration changes.

•Use the commit command to save the configuration

changes to the running configuration file and remain

within the configuration session.

Command or Action Purpose

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Cisco IOS XR Routing Configuration Guide

DETAILED STEPS

Command or Action Purpose

Step 1 configure

Example:

RP/0/RP0/CPU0:router# configure

Enters global configuration mode.

Step 2 router bgp

autonomous-system-number

Example:

RP/0/RP0/CPU0:router(config)# router bgp 120

Enters BGP configuration mode allowing you to configure

the BGP routing process.

Step 3 address-family {ipv4 unicast | ipv4 multicast |

ipv6 unicast | ipv6 multicast}

Example:

RP/0/RP0/CPU0:router(config-bgp)#

address-family ipv4 unicast

Enters global address family configuration mode for the

IPv4 address family.

Step 4 distance bgp

external-distance

internal-distance local-distance

Example:

RP/0/RP0/CPU0:router(config-bgp-af)# distance

bgp 20 20 200

Sets the external, internal, and local administrative

distances to prefer one class of routes over another. The

higher the value, the lower the trust rating. The

external-distance argument is set to 20, the

internal-distance argument is set to 20, and the

local-distance argument is set to 200.

Step 5 end

commit

Example:

RP/0/RP0/CPU0:router(config-bgp-af)# end

RP/0/RP0/CPU0:router(config-bgp-af)# commit

Saves configuration changes.

•When you issue the end command, the system prompts

you to commit changes:

Uncommitted changes found, commit them before

exiting(yes/no/cancel)?

[cancel]:

–

Entering yes saves configuration changes to the

running configuration file, exits the configuration

session, and returns the router to EXEC mode.

–

Entering no exits the configuration session and

returns the router to EXEC mode without

committing the configuration changes.

–

Entering cancel leaves the router in the current

configuration session without exiting or

committing the configuration changes.

•Use the commit command to save the configuration

changes to the running configuration file and remain

within the configuration session.

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Cisco IOS XR Routing Configuration Guide

Configuring a BGP Neighbor Group

Perform this task to configure BGP neighbor groups and apply the neighbor group configuration to a

neighbor.

After a neighbor group is configured, each neighbor can inherit the configuration through the use

command. If a neighbor is configured to use a neighbor group, the neighbor (by default) inherits the

entire configuration of the neighbor group, which includes the address family-independent and address

family-dependent configurations. The inherited configuration can be overridden if you directly

configure commands for the neighbor or configure session groups or address family groups through the

use command.

From neighbor group configuration mode, you can configure address family-independent parameters for

the neighbor group. Use the address-family command when in the neighbor group configuration mode.

After specifying the neighbor group name using the neighbor group command, you can assign options

to the neighbor group.

SUMMARY STEPS

1. configure

2. router bgp autonomous-system-number

3. neighbor-group name

4. remote-as autonomous-system-number

5. advertisement-interval seconds

6. description text

7. dmz-link-bandwidth

8. ebgp-multihop [ttl-value]

9. local-as autonomous-system-number

10. password {clear | encrypted} password

11. password-disable

12. receive-buffer-size socket-size [bgp-size]

13. send-buffer-size socket-size [bgp-size]

14. timers keepalive hold-time

15. ttl-security

16. update-source interface-type interface-number

17. exit

18. neighbor ip-address

19. use neighbor-group group-name

20. end

commit

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Cisco IOS XR Routing Configuration Guide

DETAILED STEPS

Command or Action Purpose

Step 1 configure

Example:

RP/0/RP0/CPU0:router# configure

Enters global configuration mode.

Step 2 router bgp

autonomous-system-number

Example:

RP/0/RP0/CPU0:router(config)# router bgp 120

Enters BGP configuration mode allowing you to configure

the BGP routing process.

Step 3 neighbor-group

name

Example:

RP/0/RP0/CPU0:router(config-bgp)#

neighbor-group nbr-grp-A

Places the router in neighbor group configuration mode.

Step 4 remote-as

autonomous-system-number

Example:

RP/0/RP0/CPU0:router(config-bgp-nbrgrp)#

remote-as 2002

Creates a neighbor and assigns it a remote autonomous

system number of 2002.

Step 5 advertisement-interval

seconds

Example:

RP/0/RP0/CPU0:router(config-bgp-nbrgrp)#

advertisement-interval 10

(Optional) Sets the minimum time between sending BGP

routing updates to 10 seconds.

Step 6 description

text

Example:

RP/0/RP0/CPU0:router(config-bgp-nbrgrp)#

description Neighbor on BGP 120

(Optional) Configures the description “Neighbor on BGP

120” for neighbor group nbr-grp-A.

Step 7 dmz-link-bandwidth

Example:

RP/0/RP0/CPU0:router(config-bgp-nbrgrp)#

dmz-link-bandwidth

(Optional) Advertises the bandwidth of links on router bgp

120.

Step 8 ebgp-multihop [

ttl-value

]

Example:

RP/0/RP0/CPU0:router(config-bgp-nbrgrp)#

ebgp-multihop

(Optional) Allows a BGP connection to neighbor group

nbr-grp-A.

Step 9 local-as

autonomous-system-number

Example:

RP/0/RP0/CPU0:router(config-bgp-nbrgrp)#

local-as 30

(Optional) Specifies that BGP use autonomous system 30

for the purpose of peering with neighbor group nbr-grp-A.

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Cisco IOS XR Routing Configuration Guide

Step 10 password {clear | encrypted}

password

Example:

RP/0/RP0/CPU0:router(config-bgp-nbrgrp)#

password clear pswd123

(Optional) Configures neighbor group nbr-grp-A to use

MD5 authentication with the password pswd123.

Step 11 password-disable

Example:

RP/0/RP0/CPU0:router(config-bgp-nbrgrp)#

password-disable

(Optional) Overrides any inherited password configuration

from the neighbor group.

Step 12 receive-buffer-size

socket-size

[

bgp-size

]

Example:

RP/0/RP0/CPU0:router(config-bgp-nbrgrp)#

receive-buffer-size 45215 5156

(Optional) Sets the receive buffer sizes for neighbor group

nbr-grp-A to 45215 bytes for the socket buffer and 5156

bytes for the BGP buffer.

Step 13 send-buffer-size

socket-size

[

bgp-size

]

Example:

RP/0/RP0/CPU0:router(config-bgp-nbrgrp)#

send-buffer-size 8741 8741

(Optional) Sets the send buffer sizes for neighbor group

nbr-grp-A to 8741 bytes for the socket buffer and 8741

bytes for the BGP buffer.

Step 14 timers

keepalive hold-time

Example:

RP/0/RP0/CPU0:router(config-bgp-nbrgrp)# timers

60 220

(Optional) Sets the keepalive timer to 60 seconds and the

hold-time timer to 220 seconds for the BGP neighbor group

nbr-grp-A.

Step 15 ttl-security

Example:

RP/0/RP0/CPU0:router(config-bgp-nbrgrp)#

ttl-security

(Optional) Enables TTL security for eBGP neighbor group

nbr-grp-A.

Step 16 update-source

interface-type interface-number

Example:

RP/0/RP0/CPU0:router(config-bgp-nbrgrp)#

update-source Loopback0

(Optional) Configures the router to use the IP address from

the Loopback0 interface when trying to open a session with

neighbor group nbr-grp-A.

Step 17 exit

Example:

RP/0/RP0/CPU0:router(config-bgp-nbrgrp)# exit

Exits the current configuration mode.

Step 18 neighbor

ip-address

Example:

RP/0/RP0/CPU0:router(config-bgp)# neighbor

172.168.40.24

Places the router in neighbor configuration mode for BGP

routing and configures the neighbor IP address

172.168.40.24 as a BGP peer.

Command or Action Purpose

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Cisco IOS XR Routing Configuration Guide

Configuring a BGP Neighbor

Perform this task to configure BGP neighbors.

SUMMARY STEPS

1. configure

2. router bgp autonomous-system-number

3. neighbor ip-address

4. remote-as autonomous-system-number

5. address-family {ipv4 unicast | ipv4 multicast | ipv6 unicast | ipv6 multicast}

6. end

commit

Step 19 use neighbor-group

group-name

Example:

RP/0/RP0/CPU0:router(config-bgp-nbr)# use

neighbor-group nbr-grp-A

(Optional) Specifies that BGP neighbor 172.168.40.24

inherit configuration from neighbor group nbr-grp-A.

Step 20 end

commit

Example:

RP/0/RP0/CPU0:router(config-bgp-nbr)# end

RP/0/RP0/CPU0:router(config-bgp-nbr)# commit

Saves configuration changes.

•When you issue the end command, the system prompts

you to commit changes:

Uncommitted changes found, commit them before

exiting(yes/no/cancel)?

[cancel]:

–

Entering yes saves configuration changes to the

running configuration file, exits the configuration

session, and returns the router to EXEC mode.

–

Entering no exits the configuration session and

returns the router to EXEC mode without

committing the configuration changes.

–

Entering cancel leaves the router in the current

configuration session without exiting or

committing the configuration changes.

•Use the commit command to save the configuration

changes to the running configuration file and remain

within the configuration session.

Command or Action Purpose

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Cisco IOS XR Routing Configuration Guide

DETAILED STEPS

Command or Action Purpose

Step 1 configure

Example:

RP/0/RP0/CPU0:router# configure

Enters global configuration mode.

Step 2 router bgp

autonomous-system-number

Example:

RP/0/RP0/CPU0:router(config)# router bgp 120

Enters BGP configuration mode allowing you to configure

the BGP routing process.

Step 3 neighbor

ip-address

Example:

RP/0/RP0/CPU0:router(config-bgp)# neighbor

172.168.40.24

Places the router in neighbor configuration mode for BGP

routing and configures the neighbor IP address

172.168.40.24 as a BGP peer.

Step 4 remote-as

autonomous-system-number

Example:

RP/0/RP0/CPU0:router(config-bgp-nbr)# remote-as

2002

Creates a neighbor and assigns it a remote autonomous

system number of 2002.

Step 5 address-family {ipv4 unicast | ipv4 multicast |

ipv6 unicast | ipv6 multicast}

Example:

RP/0/RP0/CPU0:router(config-bgp-nbr)#

address-family ipv4 unicast

Enters neighbor address family configuration mode for the

IPv4 address family.

Step 6 end

commit

Example:

RP/0/RP0/CPU0:router(config-bgp-nbr-af)# end

RP/0/RP0/CPU0:router(config-bgp-nbr-af)# commit

Saves configuration changes.

•When you issue the end command, the system prompts

you to commit changes:

Uncommitted changes found, commit them before

exiting(yes/no/cancel)?

[cancel]:

–

Entering yes saves configuration changes to the

running configuration file, exits the configuration

session, and returns the router to EXEC mode.

–

Entering no exits the configuration session and

returns the router to EXEC mode without

committing the configuration changes.

–

Entering cancel leaves the router in the current

configuration session without exiting or

committing the configuration changes.

•Use the commit command to save the configuration

changes to the running configuration file and remain

within the configuration session.

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Cisco IOS XR Routing Configuration Guide

Configuring a Route Reflector for BGP

Perform this task to configure a route reflector for BGP.

All the neighbors configured with the route-reflector-client command are members of the client group,

and the remaining iBGP peers are members of the nonclient group for the local route reflector.

Together, a route reflector and its clients form a cluster. A cluster of clients usually has a single route

reflector. In such instances, the cluster is identified by the software as the router ID of the route reflector.

To increase redundancy and avoid a single point of failure in the network, a cluster can have more than

one route reflector. If it does, all route reflectors in the cluster must be configured with the same 4-byte

cluster ID so that a route reflector can recognize updates from route reflectors in the same cluster. The

bgp cluster-id command is used to configure the cluster ID when the cluster has more than one route

reflector.

SUMMARY STEPS

1. configure

2. router bgp autonomous-system-number

3. bgp cluster-id cluster-id

4. neighbor ip-address

5. remote-as autonomous-system-number

6. address-family {ipv4 unicast | ipv4 multicast | ipv6 unicast | ipv6 multicast}

7. route-reflector-client

8. end

commit

DETAILED STEPS

Command or Action Purpose

Step 1 configure

Example:

RP/0/RP0/CPU0:router# configure

Enters global configuration mode.

Step 2 router bgp

autonomous-system-number

Example:

RP/0/RP0/CPU0:router(config)# router bgp 120

Enters BGP configuration mode allowing you to configure

the BGP routing process.

Step 3 bgp cluster-id

cluster-id

Example:

RP/0/RP0/CPU0:router(config-bgp)# bgp

cluster-id 192.168.70.1

Configures the local router as one of the route reflectors

serving the cluster. It is configured with the cluster ID of

192.168.70.1 to identify the cluster.

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Cisco IOS XR Routing Configuration Guide

Step 4 neighbor

ip-address

Example:

RP/0/RP0/CPU0:router(config-bgp)# neighbor

172.168.40.24

Places the router in neighbor configuration mode for BGP

routing and configures the neighbor IP address

172.168.40.24 as a BGP peer.

Step 5 remote-as

autonomous-system-number

Example:

RP/0/RP0/CPU0:router(config-bgp-nbr)# remote-as

2002

Creates a neighbor and assigns it a remote autonomous

system number of 2002.

Step 6 address-family {ipv4 unicast | ipv4 multicast |

ipv6 unicast | ipv6 multicast}

Example:

RP/0/RP0/CPU0:router(config-bgp-nbr)#

address-family ipv4 unicast

Enters neighbor address family configuration mode for the

IPv4 address family.

Step 7 route-reflector-client

Example:

RP/0/RP0/CPU0:router(config-bgp-nbr-af)#

route-reflector-client

Configures the router as a BGP route reflector and

configures the neighbor 172.168.40.24 as its client.

Step 8 end

commit

Example:

RP/0/RP0/CPU0:router(config-bgp-nbr-af)# end

RP/0/RP0/CPU0:router(config-bgp-nbr-af)# commit

Saves configuration changes.

•When you issue the end command, the system prompts

you to commit changes:

Uncommitted changes found, commit them before

exiting(yes/no/cancel)?

[cancel]:

–

Entering yes saves configuration changes to the

running configuration file, exits the configuration

session, and returns the router to EXEC mode.

–

Entering no exits the configuration session and

returns the router to EXEC mode without

committing the configuration changes.

–

Entering cancel leaves the router in the current

configuration session without exiting or

committing the configuration changes.

•Use the commit command to save the configuration

changes to the running configuration file and remain

within the configuration session.

Command or Action Purpose

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Cisco IOS XR Routing Configuration Guide

Configuring BGP Route Filtering by Route Policy

Perform this task to configure BGP routing filtering by route policy.

Prerequisites

See the Implementing Routing Policy on Cisco IOS XR Software module of the Cisco IOS XR Routing

Configuration Guide for a list of the supported attributes and operations that are valid for inbound and

outbound neighbor policy filtering.

SUMMARY STEPS

1. configure

2. route-policy name

3. end-policy

4. router bgp autonomous-system-number

5. neighbor ip-address

6. address-family {ipv4 unicast | ipv4 multicast | ipv6 unicast | ipv6 multicast}

7. route-policy route-policy-name {in | out}

8. end

commit

DETAILED STEPS

Command or Action Purpose

Step 1 configure

Example:

RP/0/RP0/CPU0:router# configure

Enters global configuration mode.

Step 2 route-policy

name

Example:

RP/0/RP0/CPU0:router(config)# route-policy

drop-as-1234

RP/0/RP0/CPU0:router(config-rpl)# if as-path

passes-through '1234' then

RP/0/RP0/CPU0:router(config-rpl)# apply

check-communities

RP/0/RP0/CPU0:router(config-rpl)# else

RP/0/RP0/CPU0:router(config-rpl)# pass

RP/0/RP0/CPU0:router(config-rpl)# endif

(Optional) Defines a route policy named drop-as-1234 and

enters route policy configuration mode.

Step 3 end-policy

Example:

RP/0/RP0/CPU0:router(config-rpl)# end-policy

(Optional) Ends the definition of a route policy and exits

route policy configuration mode.

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Step 4 router bgp

autonomous-system-number

Example:

RP/0/RP0/CPU0:router(config)# router bgp 120

Enters BGP configuration mode allowing you to configure

the BGP routing process.

Step 5 neighbor

ip-address

Example:

RP/0/RP0/CPU0:router(config-bgp)# neighbor

172.168.40.24

Places the router in neighbor configuration mode for BGP

routing and configures the neighbor IP address

172.168.40.24 as a BGP peer.

Step 6 address-family {ipv4 unicast | ipv4 multicast |

ipv6 unicast | ipv6 multicast}

Example:

RP/0/RP0/CPU0:router(config-bgp-nbr)#

address-family ipv4 unicast

Enters neighbor address family configuration mode for the

IPv4 address family.

Step 7 route-policy

route-policy-name

{in | out}

Example:

RP/0/RP0/CPU0:router(config-bgp-nbr-af)#

route-policy In-Ipv4 in

Applies the In-Ipv4 policy to inbound IPv4 unicast routes.

Step 8 end

commit

Example:

RP/0/RP0/CPU0:router(config-bgp-nbr-af)# end

RP/0/RP0/CPU0:router(config-bgp-nbr-af)# commit

Saves configuration changes.

•When you issue the end command, the system prompts

you to commit changes:

Uncommitted changes found, commit them before

exiting(yes/no/cancel)?

[cancel]:

–

Entering yes saves configuration changes to the

running configuration file, exits the configuration

session, and returns the router to EXEC mode.

–

Entering no exits the configuration session and

returns the router to EXEC mode without

committing the configuration changes.

–

Entering cancel leaves the router in the current

configuration session without exiting or

committing the configuration changes.

•Use the commit command to save the configuration

changes to the running configuration file and remain

within the configuration session.

Command or Action Purpose

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Cisco IOS XR Routing Configuration Guide

Disabling Next Hop Processing on BGP Updates

Perform this task to disable next hop calculation for a neighbor and insert your own address in the next

hop field of BGP updates. Disabling the calculation of the best next hop to use when advertising a route

causes all routes to be advertised with the network device as the next hop.

Note Next hop processing can be disabled for address family group, neighbor group, or neighbor address

family.

SUMMARY STEPS

1. configure

2. router bgp autonomous-system-number

3. neighbor ip-address

4. remote-as autonomous-system-number

5. address-family {ipv4 unicast | ipv4 multicast | ipv6 unicast | ipv6 multicast}

6. next-hop-self

7. end

commit

DETAILED STEPS

Command or Action Purpose

Step 1 configure

Example:

RP/0/RP0/CPU0:router# configure

Enters global configuration mode.

Step 2 router bgp

autonomous-system-number

Example:

RP/0/RP0/CPU0:router(config)# router bgp 120

Enters BGP configuration mode allowing you to configure

the BGP routing process.

Step 3 neighbor

ip-address

Example:

RP/0/RP0/CPU0:router(config-bgp)# neighbor

172.168.40.24

Places the router in neighbor configuration mode for BGP

routing and configures the neighbor IP address

172.168.40.24 as a BGP peer.

Step 4 remote-as

autonomous-system-number

Example:

RP/0/RP0/CPU0:router(config-bgp-nbr)# remote-as

2002

Creates a neighbor and assigns it a remote autonomous

system number of 2002.

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Cisco IOS XR Routing Configuration Guide

Configuring BGP Community and Extended-Community Filtering

Perform this task to specify that community attributes should be sent to an eBGP neighbor.

Perform this task to specify that community/extended-community attributes should be sent to an eBGP

neighbor. These attributes are not sent to an eBGP neighbor by default. By contrast, they are always sent

to iBGP neighbors. This section provides examples on how to enable sending community attributes. The

send-community-ebgp keyword can be replaced by the send-extended-community-ebgp keyword to

enable sending extended-communities.

Note If the send-community-ebgp command is configured for a neighbor group or address family group, all

neighbors using the group inherit the configuration. Configuring the command specifically for a

neighbor overrides inherited values.

Step 5 address-family {ipv4 unicast | ipv4 multicast |

ipv6 unicast | ipv6 multicast}

Example:

RP/0/RP0/CPU0:router(config-bgp-nbr)#

address-family ipv4 unicast

Enters neighbor address family configuration mode for the

IPv4 address family.

Step 6 next-hop-self

Example:

RP/0/RP0/CPU0:router(config-bgp-nbr-af)#

next-hop-self

Sets the next hop attribute for all IPv4 unicast routes

advertised to neighbor 172.168.40.24 to the address of the

local router. Disabling the calculation of the best next hop

to use when advertising a route causes all routes to be

advertised with the local network device as the next hop.

Step 7 end

commit

Example:

RP/0/RP0/CPU0:router(config-bgp-nbr-af)# end

RP/0/RP0/CPU0:router(config-bgp-nbr-af)# commit

Saves configuration changes.

•When you issue the end command, the system prompts

you to commit changes:

Uncommitted changes found, commit them before

exiting(yes/no/cancel)?

[cancel]:

–

Entering yes saves configuration changes to the

running configuration file, exits the configuration

session, and returns the router to EXEC mode.

–

Entering no exits the configuration session and

returns the router to EXEC mode without

committing the configuration changes.

–

Entering cancel leaves the router in the current

configuration session without exiting or

committing the configuration changes.

•Use the commit command to save the configuration

changes to the running configuration file and remain

within the configuration session.

Command or Action Purpose

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Cisco IOS XR Routing Configuration Guide

SUMMARY STEPS

1. configure

2. router bgp autonomous-system-number

3. neighbor ip-address

4. remote-as autonomous-system-number

5. address-family {ipv4 unicast | ipv4 multicast | ipv6 unicast | ipv6 multicast}

6. send-community-ebgp

7. end

commit

DETAILED STEPS

Command or Action Purpose

Step 1 configure

Example:

RP/0/RP0/CPU0:router# configure

Enters global configuration mode.

Step 2 router bgp

autonomous-system-number

Example:

RP/0/RP0/CPU0:router(config)# router bgp 120

Enters BGP configuration mode allowing you to configure

the BGP routing process.

Step 3 neighbor

ip-address

Example:

RP/0/RP0/CPU0:router(config-bgp)# neighbor

172.168.40.24

Places the router in neighbor configuration mode for BGP

routing and configures the neighbor IP address

172.168.40.24 as a BGP peer.

Step 4 remote-as

autonomous-system-number

Example:

RP/0/RP0/CPU0:router(config-bgp-nbr)# remote-as

2002

Creates a neighbor and assigns it a remote autonomous

system number of 2002.

Step 5 address-family {ipv4 unicast | ipv4 multicast |

ipv6 unicast | ipv6 multicast}

Example:

RP/0/RP0/CPU0:router(config-bgp-nbr)#

address-family ipv4 unicast

Enters neighbor address family configuration mode for the

IPv4 address family.

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Configuring Software to Store Updates from a Neighbor

Perform this task to configure the software to store updates received from a neighbor.

The soft-reconfiguration inbound command causes a route refresh request to be sent to the neighbor if

the neighbor is route refresh capable. If the neighbor is not route refresh capable, the neighbor must be

reset to relearn received routes using the clear bgp soft command. See the “Resetting Neighbors Using

BGP Dynamic Inbound Soft Reset” section on page RC-71.

Note Storing updates from a neighbor works only if either the neighbor is route refresh capable or if the

soft-reconfiguration inbound command is configured. Even if the neighbor is route refresh capable and

the soft-reconfiguration inbound command is configured, the original routes are not stored unless the

always option is used with the command. The original routes can be easily retrieved with a route refresh

request. Route refresh sends a request to the peer to resend its routing information. The

soft-reconfiguration inbound command stores all paths received from the peer in an unmodified form

and refers to these stored paths during the clear. Soft reconfiguration is memory intensive.

SUMMARY STEPS

1. configure

2. router bgp autonomous-system-number

3. neighbor ip-address

Step 6 send-community-ebgp

Example:

RP/0/RP0/CPU0:router(config-bgp-nbr-af)#

send-community-ebgp

Specifies that the router send community attributes (which

are disabled by default for eBGP neighbors) to eBGP

neighbor 172.168.40.24 for IPv4 multicast routes.

Step 7 end

commit

Example:

RP/0/RP0/CPU0:router(config-bgp-nbr-af)# end

RP/0/RP0/CPU0:router(config-bgp-nbr-af)# commit

Saves configuration changes.

•When you issue the end command, the system prompts

you to commit changes:

Uncommitted changes found, commit them before

exiting(yes/no/cancel)?

[cancel]:

–

Entering yes saves configuration changes to the

running configuration file, exits the configuration

session, and returns the router to EXEC mode.

–

Entering no exits the configuration session and

returns the router to EXEC mode without

committing the configuration changes.

–

Entering cancel leaves the router in the current

configuration session without exiting or

committing the configuration changes.

•Use the commit command to save the configuration

changes to the running configuration file and remain

within the configuration session.

Command or Action Purpose

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4. address-family {ipv4 unicast | ipv4 multicast | ipv6 unicast | ipv6 multicast}

5. soft-reconfiguration inbound always

6. end

commit

DETAILED STEPS

Command or Action Purpose

Step 1 configure

Example:

RP/0/RP0/CPU0:router# configure

Enters global configuration mode.

Step 2 router bgp

autonomous-system-number

Example:

RP/0/RP0/CPU0:router(config)# router bgp 120

Enters BGP configuration mode allowing you to configure

the BGP routing process.

Step 3 neighbor

ip-address

Example:

RP/0/RP0/CPU0:router(config-bgp)# neighbor

172.168.40.24

Places the router in neighbor configuration mode for BGP

routing and configures the neighbor IP address

172.168.40.24 as a BGP peer.

Step 4 address-family {ipv4 unicast | ipv4 multicast |

ipv6 unicast | ipv6 multicast}

Example:

RP/0/RP0/CPU0:router(config-bgp-nbr)#

address-family ipv4 unicast

Enters neighbor address family configuration mode for the

IPv4 address family.

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Disabling a BGP Neighbor

Perform this task to administratively shut down a neighbor without removing the configuration.

SUMMARY STEPS

1. configure

2. router bgp autonomous-system-number

3. neighbor ip-address

4. shutdown

5. end

commit

Step 5 soft-reconfiguration inbound always

Example:

RP/0/RP0/CPU0:router(config-bgp-nbr-af)#

soft-reconfiguration inbound always

Configures the software to store updates received from

neighbor 172.168.40.24. Soft reconfiguration inbound

causes the software to store the original unmodified route in

addition to a route that is modified or filtered. This allows a

“soft clear” to be performed after the inbound policy is

changed.

Step 6 end

commit

Example:

RP/0/RP0/CPU0:router(config-bgp-nbr-af)# end

RP/0/RP0/CPU0:router(config-bgp-nbr-af)# commit

Saves configuration changes.

•When you issue the end command, the system prompts

you to commit changes:

Uncommitted changes found, commit them before

exiting(yes/no/cancel)?

[cancel]:

–

Entering yes saves configuration changes to the

running configuration file, exits the configuration

session, and returns the router to EXEC mode.

–

Entering no exits the configuration session and

returns the router to EXEC mode without

committing the configuration changes.

–

Entering cancel leaves the router in the current

configuration session without exiting or

committing the configuration changes.

•Use the commit command to save the configuration

changes to the running configuration file and remain

within the configuration session.

Command or Action Purpose

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DETAILED STEPS

Command or Action Purpose

Step 1 configure

Example:

RP/0/RP0/CPU0:router# configure

Enters global configuration mode.

Step 2 router bgp

autonomous-system-number

Example:

RP/0/RP0/CPU0:router(config)# router bgp 120

Enters BGP configuration mode allowing you to configure

the BGP routing process.

Step 3 neighbor

ip-address

Example:

RP/0/RP0/CPU0:router(config-bgp)# neighbor

172.168.40.24

Places the router in neighbor configuration mode for BGP

routing and configures the neighbor IP address

172.168.40.24 as a BGP peer.

Step 4 shutdown

Example:

RP/0/RP0/CPU0:router(config-bgp-nbr)# shutdown

Disables all active sessions for neighbor 172.168.40.24.

Step 5 end

commit

Example:

RP/0/RP0/CPU0:router(config-bgp-nbr)# end

RP/0/RP0/CPU0:router(config-bgp-nbr)# commit

Saves configuration changes.

•When you issue the end command, the system prompts

you to commit changes:

Uncommitted changes found, commit them before

exiting(yes/no/cancel)?

[cancel]:

–

Entering yes saves configuration changes to the

running configuration file, exits the configuration

session, and returns the router to EXEC mode.

–

Entering no exits the configuration session and

returns the router to EXEC mode without

committing the configuration changes.

–

Entering cancel leaves the router in the current

configuration session without exiting or

committing the configuration changes.

•Use the commit command to save the configuration

changes to the running configuration file and remain

within the configuration session.

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Resetting Neighbors Using BGP Dynamic Inbound Soft Reset

Perform this task to trigger an inbound soft reset of the specified address families for the specified group or

neighbors.

Resetting neighbors is useful if you change the inbound policy for the neighbors or any other

configuration that affects the sending or receiving of routing updates. If an inbound soft reset is

triggered, BGP sends a REFRESH request to the neighbor if the neighbor has advertised the

ROUTE_REFRESH capability. To determine whether the neighbor has advertised the

ROUTE_REFRESH capability, use the show bgp neighbors command.

SUMMARY STEPS

1. show bgp neighbors

2. clear bgp {ipv4 | ipv6 | all} {unicast | multicast | all} {* | ip-address | as-number | external} soft in

DETAILED STEPS

Resetting Neighbors Using BGP Outbound Soft Reset

Perform this task to trigger an outbound soft reset of the specified address families for the specified group

or neighbors.

Resetting neighbors is useful if you change the outbound policy for the neighbors or any other

configuration that affects the sending or receiving of routing updates.

If an outbound soft reset is triggered, BGP resends all routes for the address family to the given

neighbors.

To determine whether the neighbor has advertised the ROUTE_REFRESH capability, use the show bgp

neighbors command.

Command or Action Purpose

Step 1 show bgp neighbors

Example:

RP/0/RP0/CPU0:router# show bgp neighbors

Verifies that received route refresh capability from the

neighbor is enabled.

Step 2 clear bgp {ipv4 | ipv6 | all} {unicast |

multicast | all} {* |

ip-address

as-number

external} soft in

Example:

RP/0/RP0/CPU0:router# clear bgp ipv4 unicast

10.0.0.1 soft in

Soft resets a BGP neighbor.

•The * keyword resets all BGP neighbors.

•The ip-address argument specifies the address of the

neighbor to be reset.

•The as-number argument specifies that all neighbors

that match the autonomous system number be reset.

•The external keyword specifies that all external

neighbors are reset.

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SUMMARY STEPS

1. show bgp neighbors

2. clear bgp {ipv4 | ipv6 | all} {unicast | multicast | all} {* | ip-address | as-number | external} soft

out

DETAILED STEPS

Resetting Neighbors Using BGP Hard Reset

Perform this task to reset neighbors using a hard reset. A hard reset removes the TCP connection to the

neighbor, removes all routes received from the neighbor from the BGP table, and then re-establishes the

session with the neighbor. If the graceful keyword is specified, the routes from the neighbor are not

removed from the BGP table immediately, but are marked as stale. After the session is re-established,

any stale route that has not been received again from the neighbor is removed.

SUMMARY STEPS

1. clear bgp {* | ip-address | as-number | external} [graceful]

DETAILED STEPS

Command or Action Purpose

Step 1 show bgp neighbors

Example:

RP/0/RP0/CPU0:router# show bgp neighbors

Verifies that received route refresh capability from the

neighbor is enabled.

Step 2 clear bgp {ipv4 | ipv6 | all} {unicast |

multicast | all} {* |

ip-address

as-number

external} soft out

Example:

RP/0/RP0/CPU0:router# clear bgp ipv4 unicast

10.0.0.2 soft out

Soft resets a BGP neighbor.

•The * keyword resets all BGP neighbors.

•The ip-address argument specifies the address of the

neighbor to be reset.

•The as-number argument specifies that all neighbors

that match the autonomous system number be reset.

•The external keyword specifies that all external

neighbors are reset.

Command or Action Purpose

Step 1 clear bgp {* |

ip-address

as-number

external} [graceful]

Example:

RP/0/RP0/CPU0:router# clear bgp 10.0.0.3

Clears a BGP neighbor. The graceful keyword specifies a

graceful restart.

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Clearing Caches, Tables and Databases

Perform this task to remove all contents of a particular cache, table, or database. Clearing a cache, table,

or database can become necessary when the contents of the particular structure have become, or are

suspected to be, invalid.

SUMMARY STEPS

1. clear bgp ip-address

2. clear bgp external

3. clear bgp *

DETAILED STEPS

Displaying System and Network Statistics

Perform this task to display specific statistics, such as the contents of BGP routing tables, caches, and

databases. Information provided can be used to determine resource usage and solve network problems.

You can also display information about node reachability and discover the routing path that the packets

of your device are taking through the network.

SUMMARY STEPS

1. show bgp cidr-only

2. show bgp count-only

3. show bgp community community-list [exact-match]

4. show bgp regexp regular-expression

5. show bgp

6. show bgp neighbors ip-address [advertised-routes | dampened-routes | flap-statistics |

performance-statistics | received prefix-filter | routes]

7. show bgp paths

Command or Action Purpose

Step 1 clear bgp

ip-address

Example:

RP/0/RP0/CPU0:router# clear bgp 172.20.1.1

Clears neighbor 172.20.1.1.

Step 2 clear bgp external

Example:

RP/0/RP0/CPU0:router# clear bgp external

Clears all external peers.

Step 3 clear bgp *

Example:

RP/0/RP0/CPU0:router# clear bgp *

Clears all BGP neighbors.

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8. show bgp neighbor-group group-name configuration

9. show bgp summary

DETAILED STEPS

Command or Action Purpose

Step 1 show bgp cidr-only

Example:

RP/0/RP0/CPU0:router# show bgp cidr-only

Displays routes with nonnatural network masks (classless

interdomain routing [CIDR]) routes.

Step 2 show bgp count-only

Example:

RP/0/RP0/CPU0:router# show bgp count-only

Displays the number of paths.

Step 3 show bgp community

community-list

[exact-match]

Example:

RP/0/RP0/CPU0:router# show bgp community 1081:5

exact-match

Displays routes that match the BGP community 1081:5.

Step 4 show bgp regexp

regular-expression

Example:

RP/0/RP0/CPU0:router# show bgp regexp "^3 "

Displays routes that match the autonomous system path

regular expression "^3 ".

Step 5 show bgp

Example:

RP/0/RP0/CPU0:router# show bgp

Displays entries in the BGP routing table.

Step 6 show bgp neighbors

ip-address

[advertised-routes | dampened-routes |

flap-statistics | performance-statistics |

received

prefix-filter

| routes]

Example:

RP/0/RP0/CPU0:router# show bgp neighbors

10.0.101.1

Displays information about the BGP connection to neighbor

10.0.101.1.

•The advertised-routes keyword displays all routes the

router advertised to the neighbor.

•The dampened-routes keyword displays the dampened

routes that are learned from the neighbor.

•The flap-statistics keyword displays flap statistics of

the routes learned from the neighbor.

•The performance-statistics keyword displays

performance statistics relating to work done by the

BGP process for this neighbor.

•The received prefix-filter keyword and argument

display the received prefix list filter.

•The routes keyword displays routes learned from the

neighbor.

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Monitoring BGP Update Groups

This task displays information related to the processing of BGP update groups.

SUMMARY STEPS

1. show bgp [{ipv4 | ipv6 | all} {unicast | multicast | all]} update-group [neighbor ip-address |

process-id.index [summary | performance-statistics]]

DETAILED STEPS

Step 7 show bgp paths

Example:

RP/0/RP0/CPU0:router# show bgp paths

Displays all BGP paths in the database.

Step 8 show bgp neighbor-group

group-name

configuration

Example:

RP/0/RP0/CPU0:router# show bgp neighbor-group

group_1 configuration

Displays the effective configuration for neighbor group

group_1, including any configuration inherited by this

neighbor group.

Step 9 show bgp summary

Example:

RP/0/RP0/CPU0:router# show bgp summary

Displays the status of all BGP connections.

Command or Action Purpose

Step 1 show bgp [{ipv4 | ipv6 | all} {unicast |

multicast | all}] update-group [neighbor

ip-address

process-id.index

[summary |

performance-statistics]]

Example:

RP/0/RP0/CPU0:router# show bgp update-group 0.0

Displays information about BGP update groups.

•The ip-address argument displays the update groups to

which that neighbor belongs.

•The process-id.index argument selects a particular

update group to display and is specified as follows:

process id (dot) index. Process ID range is from 0 to

254. Index range is from 0 to 4294967295.

•The summary keyword displays summary information

for neighbors in a particular update group.

•If no argument is specified, this command displays

information for all update groups (for the specified

address family).

•The performance-statistics keyword displays

performance statistics for an update group.

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Configuration Examples for Implementing BGP on Cisco IOS XR

Software

This section provides the following configuration examples:

•Enabling BGP: Example, page RC-76

•Displaying BGP Update Groups: Example, page RC-77

•BGP Neighbor Configuration: Example, page RC-78

•BGP Confederation: Example, page RC-78

•BGP Route Reflector: Example, page RC-79

Enabling BGP: Example

The following shows how to enable BGP.

prefix-set static

2020::/64,

2012::/64,

10.10.0.0/16,

10.2.0.0/24

end-set

route-policy pass-all

pass

end-policy

route-policy set_next_hop_agg_v4

set next-hop 10.0.0.1

end-policy

route-policy set_next_hop_static_v4

if (destination in static) then

set next-hop 10.1.0.1

else

drop

endif

end-policy

route-policy set_next_hop_agg_v6

set next-hop 2003::121

end-policy

route-policy set_next_hop_static_v6

if (destination in static) then

set next-hop 2011::121

else

drop

endif

end-policy

router bgp 65000

bgp fast-external-fallover disable

bgp confederation peers

65001

65002

bgp confederation identifier 1

bgp router-id 1.1.1.1

address-family ipv4 unicast

aggregate-address 10.2.0.0/24 route-policy set_next_hop_agg_v4

aggregate-address 10.3.0.0/24

redistribute static route-policy set_next_hop_static_v4

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address-family ipv4 multicast

aggregate-address 10.2.0.0/24 route-policy set_next_hop_agg_v4

aggregate-address 10.3.0.0/24

redistribute static route-policy set_next_hop_static_v4

address-family ipv6 unicast

aggregate-address 2012::/64 route-policy set_next_hop_agg_v6

aggregate-address 2013::/64

redistribute static route-policy set_next_hop_static_v6

address-family ipv6 multicast

aggregate-address 2012::/64 route-policy set_next_hop_agg_v6

aggregate-address 2013::/64

redistribute static route-policy set_next_hop_static_v6

neighbor 10.0.101.60

remote-as 65000

address-family ipv4 unicast

address-family ipv4 multicast

neighbor 10.0.101.61

remote-as 65000

address-family ipv4 unicast

address-family ipv4 multicast

neighbor 10.0.101.62

remote-as 3

address-family ipv4 unicast

route-policy pass-all in

route-policy pass-all out

address-family ipv4 multicast

route-policy pass-all in

route-policy pass-all out

neighbor 10.0.101.64

remote-as 5

update-source Loopback0

address-family ipv4 unicast

route-policy pass-all in

route-policy pass-all out

address-family ipv4 multicast

route-policy pass-all in

route-policy pass-all out

Displaying BGP Update Groups: Example

The following is sample output from the show bgp update-group command executed in EXEC mode:

RP/0/RP0/CPU0:router# show bgp update-group

Update group for IPv4 Unicast, index 0.1:

Attributes:

Outbound Route map:rm

Minimum advertisement interval:30

Messages formatted:2, replicated:2

Neighbors in this update group:

10.0.101.92

Update group for IPv4 Unicast, index 0.2:

Attributes:

Minimum advertisement interval:30

Messages formatted:2, replicated:2

Neighbors in this update group:

10.0.101.91

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BGP Neighbor Configuration: Example

The following example shows how BGP neighbors on an autonomous system are configured to share

information. In the example, a BGP router is assigned to autonomous system 109, and two networks are

listed as originating in the autonomous system. Then the addresses of three remote routers (and their

autonomous systems) are listed. The router being configured shares information about networks

131.108.0.0 and 192.31.7.0 with the neighbor routers. The first router listed is in a different autonomous

system; the second neighbor and remote-as commands specify an internal neighbor (with the same

autonomous system number) at address 131.108.234.2; and the third neighbor and remote-as

commands specify a neighbor on a different autonomous system.

router bgp 109

network 131.108.0.0

network 192.31.7.0

neighbor 131.108.200.1

remote-as 167

neighbor 131.108.234.2

remote-as 109

neighbor 150.136.64.19

remote-as 99

BGP Confederation: Example

The following is a sample configuration that shows several peers in a confederation. The confederation

consists of three internal autonomous systems with autonomous system numbers 6001, 6002, and 6003.

To the BGP speakers outside the confederation, the confederation looks like a normal autonomous

system with autonomous system number 666 (specified using the bgp confederation identifier

command).

In a BGP speaker in autonomous system 6001, the bgp confederation peers command marks the peers

from autonomous systems 6002 and 6003 as special eBGP peers. Hence, peers 171.69.232.55 and

171.69.232.56 get the local preference, next hop, and MED unmodified in the updates. The router at

160.69.69.1 is a normal eBGP speaker and the updates received by it from this peer are just like a normal

eBGP update from a peer in autonomous system 666.

router bgp 6001

bgp confederation identifier 666

bgp confederation peers 6002 6003

neighbor 171.69.232.55

remote-as 6002

neighbor 171.69.232.56

remote-as 6003

neighbor 160.69.69.1

remote-as 777

In a BGP speaker in autonomous system 6002, the peers from autonomous systems 6001 and 6003 are

configured as special eBGP peers. Peer 170.70.70.1 is a normal iBGP peer and peer 199.99.99.2 is a

normal eBGP peer from autonomous system 700.

router bgp 6002

bgp confederation identifier 666

bgp confederation peers 6001 6003

neighbor 170.70.70.1

remote-as 6002

neighbor 171.69.232.57

remote-as 6001

neighbor 171.69.232.56

remote-as 6003

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neighbor 199.99.99.2

remote-as 700

In a BGP speaker in autonomous system 6003, the peers from autonomous systems 6001 and 6002 are

configured as special eBGP peers. Peer 200.200.200.200 is a normal eBGP peer from autonomous

system 701.

router bgp 6003

bgp confederation identifier 666

bgp confederation peers 6001 6002

neighbor 171.69.232.57

remote-as 6001

neighbor 171.69.232.55

remote-as 6002

neighbor 200.200.200.200

remote-as 701

The following is a part of the configuration from the BGP speaker 200.200.200.205 from autonomous

system 701 in the same example. Neighbor 171.69.232.56 is configured as a normal eBGP speaker from

autonomous system 666. The internal division of the autonomous system into multiple autonomous

systems is not known to the peers external to the confederation.

router bgp 701

neighbor 171.69.232.56

remote-as 666

neighbor 200.200.200.205

remote-as 701

BGP Route Reflector: Example

The following example shows how to use an address family to configure internal BGP peer 10.1.1.1 as

a route reflector client for both unicast and multicast prefixes:

router bgp 140

neighbor 10.1.1.1

remote-as 140

address-family ipv4 unicast

route-reflector-client

router bgp 140

neighbor 10.1.1.1

remote-as 140

address-family ipv4 multicast

route-reflector-client

Where to Go Next

For detailed information about BGP commands, see the Cisco IOS XR Routing Command Reference

document.

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Additional References

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Additional References

The following sections provide references related to implementing BGP for Cisco IOS XR software.

Related Documents

Standards

MIBs

RFCs

Related Topic Document Title

BGP commands: complete command syntax, command

modes, command history, defaults, usage guidelines,

and examples

Cisco IOS XR Routing Command Reference, Release 3.2

Standards Title

draft-ietf-idr-bgp4-26.txt A Border Gateway Protocol 4, by Y. Rekhter, T.Li, S. Hares

draft-ietf-idr-bgp4-mib-15.txt Definitions of Managed Objects for the Fourth Version of Border

Gateway Protocol (BGP-4), by J. Hass and S. Hares

draft-ietf-idr-cease-subcode-05.txt Subcodes for BGP Cease Notification Message, by Enke Chen, V.

Gillet

MIBs MIBs Link

•BGP4-MIB

•CISCO-BGP4-MIB

To locate and download MIBs for selected platforms using

Cisco IOS XR software, use the Cisco MIB Locator found at the

following URL:

http://cisco.com/public/sw-center/netmgmt/cmtk/mibs.shtml

RFCs Title

RFC 1997 BGP Communities Attribute

RFC 2385 Protection of BGP Sessions via the TCP MD5 Signature Option

RFC 2439 BGP Route Flap Damping

RFC 2545 Use of BGP-4 Multiprotocol Extensions for IPv6 Inter-Domain

Routing

RFC 2796 BGP Route Reflection - An Alternative to Full Mesh IBGP

RFC 2858 Multiprotocol Extensions for BGP-4

RFC 2918 Route Refresh Capability for BGP-4

Implementing BGP on Cisco IOS XR Software

Additional References

RC-81

Cisco IOS XR Routing Configuration Guide

Technical Assistance

RFC 3065 Autonomous System Confederations for BGP

RFC 3392 Capabilities Advertisement with BGP-4

Description Link

The Cisco Technical Support website contains

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RFCs Title

Implementing BGP on Cisco IOS XR Software

Additional References

RC-82

Cisco IOS XR Routing Configuration Guide

RC-83

Cisco IOS XR Routing Configuration Guide

Implementing IS-IS on Cisco IOS XR Software

Integrated Intermediate System-to-Intermediate System (IS-IS), Internet Protocol Version 4 (IPv4), is a

standards-based Interior Gateway Protocol (IGP).

Cisco IOS XR implements the IP routing capabilities described in International Organization for

Standardization (ISO)/International Engineering Consortium (IEC) 10589 and RFC 1995, and adds the

standard extensions for single topology and multitopology IS-IS for IP Version 6 (IPv6).

This module describes the new and revised tasks you need to implement IS-IS (IPv4 and IPv6) on your

Cisco IOS XR network.

Note For more information about IS-IS on the Cisco IOS XR software and complete descriptions of the IS-IS

commands listed in this module, you can refer to the “Related Documents” section of this module. To

locate documentation for other commands that might appear while of executing a configuration task,

search online in the Cisco IOS XR software master command index.

Feature History for Implementing IS-IS on Cisco IOS XR Software

Contents

•Prerequisites for Implementing IS-IS on Cisco IOS XR Software, page RC-84

•Restrictions for Implementing IS-IS on Cisco IOS XR Software, page RC-84

•Information About Implementing IS-IS on Cisco IOS XR Software, page RC-84

•How to Implement IS-IS on Cisco IOS XR Software, page RC-91

•Configuration Examples for Implementing IS-IS on Cisco IOS XR Software, page RC-122

•Where to Go Next, page RC-124

•Additional References, page RC-124

Release Modification

Release 2.0 This feature was introduced on the Cisco CRS-1.

Release 3.0 No modification.

Release 3.2 Support was added for the Cisco XR 12000 Series Router. The ability to

configure a broadcast medium connecting two networking devices as a

point-to-point link was added.

Release 3.2.2 Support was added for the multicast-intact feature.

Implementing IS-IS on Cisco IOS XR Software

Prerequisites for Implementing IS-IS on Cisco IOS XR Software

RC-84

Cisco IOS XR Routing Configuration Guide

Prerequisites for Implementing IS-IS on Cisco IOS XR Software

The following are prerequisites for implementing IS-IS on Cisco IOS XR software:

•You must be in a user group associated with a task group that includes the proper task IDs for IS-IS

commands. Task IDs for commands are listed in the Cisco IOS XR Task ID Reference Guide. For

detailed information about user groups and task IDs, see the Configuring AAA Services on

Cisco IOS XR Software module of the Cisco IOS XR System Security Configuration Guide.

Restrictions for Implementing IS-IS on Cisco IOS XR Software

When multiple instances of IS-IS are being run, an interface can be associated with only one instance

(process). Instances may not share an interface. Additionally, if Multiprotocol Label Switching traffic

engineering (MPLS TE) is being employed, then MPLS must be enabled for only one instance. The

MPLS process is not multi-instance aware.

Information About Implementing IS-IS on Cisco IOS XR Software

To implement IS-IS you need to understand the following concepts:

•IS-IS Functional Overview, page RC-85

•Key Features Supported in the Cisco IOS XR IS-IS Implementation, page RC-85

•IS-IS Configuration Grouping, page RC-85

•Multitopology Configuration, page RC-86

•IPv6 Routing and Configuring IPv6 Addressing, page RC-86

•Limit LSP Flooding, page RC-86

•Maximum LSP Lifetime and Refresh Interval, page RC-87

•Overload Bit Configuration During Multitopology Operation, page RC-87

•Single-Topology IPv6 Support, page RC-87

•Multitopology IPv6 Support, page RC-88

•Nonstop Forwarding, page RC-88

•Multi-Instance IS-IS, page RC-89

•Multiprotocol Label Switching Traffic Engineering, page RC-89

•Overload Bit on Router, page RC-89

•Default Routes, page RC-90

•Attached Bit on an IS-IS Instance, page RC-90

Implementing IS-IS on Cisco IOS XR Software

Information About Implementing IS-IS on Cisco IOS XR Software

RC-85

Cisco IOS XR Routing Configuration Guide

IS-IS Functional Overview

Small IS-IS networks are typically built as a single area that includes all routers in the network. As the

network grows larger, it may be reorganized into a backbone area made up of the connected set of all

Level 2 routers from all areas, which is in turn connected to local areas. Within a local area, routers know

how to reach all system IDs. Between areas, routers know how to reach the backbone, and the backbone

routers know how to reach other areas.

The IS-IS routing protocol supports the configuration of backbone Level 2 and Level 1 areas and the

necessary support for moving routing information between the areas. Routers establish Level 1

adjacencies to perform routing within a local area (intra-area routing). Routers establish Level 2

adjacencies to perform routing between Level 1 areas (interarea routing).

For Cisco IOS XR software, each IS-IS instance can support either a single Level 1 or Level 2 area, or

one of each. By default, all IS-IS instances automatically support Level 1 and Level 2 routing. You can

change the level of routing to be performed by a particular routing instance using the is-type command.

Key Features Supported in the Cisco IOS XR IS-IS Implementation

The Cisco IOS XR implementation of IS-IS conforms to the IS-IS Version 2 specifications detailed in

RFC 1195 and the IPv6 IS-IS functionality based on the Internet Engineering Task Force (IETF) IS-IS

Working Group draft-ietf-isis-ipv6.txt document.

The following list outlines key features supported in the Cisco IOS XR implementation:

•Improved configuration syntax and enhanced show commands

•Single topology IPv6

•Multitopology

•Nonstop forwarding (NSF), both Cisco proprietary and IETF

•Three-way handshake

•Mesh groups

•Multiple IS-IS instances

•Configuration of a broadcast medium connecting two networking devices as a point-to-point link

IS-IS Configuration Grouping

Cisco IOS XR groups all of the IS-IS configuration in router configuration mode, including the portion

of the interface configurations associated with IS-IS. The grouping makes the configuration process

clearer, and eliminates some of the clutter in the global interface stanza. To display the IS-IS

configuration in its entirety, use the show isis interface command.

The command output displays the running configuration for all configured IS-IS instances, including the

interface assignments and interface attributes.

Implementing IS-IS on Cisco IOS XR Software

Information About Implementing IS-IS on Cisco IOS XR Software

RC-86

Cisco IOS XR Routing Configuration Guide

IS-IS Interfaces

IS-IS interfaces can be configured as one of the following types:

•active—advertises connected prefixes and forms adjacencies. This is the default for interfaces.

•passive—advertises connected prefixes but does not form adjacencies. The passive command is

used to configure interfaces as passive. Passive interfaces should be used sparingly for important

prefixes such as loopback addresses that need to be injected into the IS-IS domain. If many

connected prefixes need to be advertised then the redistribution of connected routes with the

appropriate policy should be used instead.

•suppressed—does not advertise connected prefixes but forms adjacencies. The suppress command

is used to configure interfaces as suppressed.

•shutdown—does not advertise connected prefixes and does not form adjacencies. The shutdown

command is used to disable interfaces without removing the IS-IS configuration.

Multitopology Configuration

Cisco IOS XR software supports multitopology for IPv6 IS-IS unless single topology is explicitly

configured in IPv6 address-family configuration mode.

Note IS-IS supports IP routing and not Open Systems Interconnection (OSI) Connectionless Network Service

(CLNS) routing.

IPv6 Routing and Configuring IPv6 Addressing

By default, IPv6 routing is disabled in the Cisco IOS XR software. To enable IPv6 routing, you must

assign IPv6 addresses to individual interfaces in the router using the ipv6 enable or ipv6 address

command. See the Network Stack IPv4 and IPv6 Commands on Cisco IOS XR Software module of the

Cisco IOS XR IP Addresses and Services Command Reference.

Limit LSP Flooding

Limiting link-state packets (LSP) may be desirable in certain “meshy” network topologies. An example

of such a network might be a highly redundant one such as a fully meshed set of point-to-point links over

a nonbroadcast multiaccess (NBMA) transport. In such networks, full LSP flooding can limit network

scalability. One way to restrict the size of the flooding domain is to introduce hierarchy by using multiple

Level 1 areas and a Level 2 area. However, two other techniques can be used instead of or with hierarchy:

Block flooding on specific interfaces and configure mesh groups.

Both techniques operate by restricting the flooding of LSPs in some fashion. A direct consequence is

that although scalability of the network is improved, the reliability of the network (in the face of failures)

is reduced because a series of failures may prevent LSPs from being flooded throughout the network,

even though links exist that would allow flooding if blocking or mesh groups had not restricted their use.

In such a case, the link-state databases of different routers in the network may no longer be synchronized.

Consequences such as persistent forwarding loops can ensue. For this reason, we recommend that

blocking or mesh groups be used only if specifically required, and then only after careful network

design.

Implementing IS-IS on Cisco IOS XR Software

Information About Implementing IS-IS on Cisco IOS XR Software

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Cisco IOS XR Routing Configuration Guide

Flood Blocking on Specific Interfaces

With this technique, certain interfaces are blocked from being used for flooding LSPs, but the remaining

interfaces operate normally for flooding. This technique is simple to understand and configure, but may

be more difficult to maintain and more error prone than mesh groups in the long run. The flooding

topology that IS-IS uses is fine-tuned rather than restricted. Restricting the topology too much (blocking

too many interfaces) makes the network unreliable in the face of failures. Restricting the topology too

little (blocking too few interfaces) may fail to achieve the desired scalability.

To improve the robustness of the network in the event that all nonblocked interfaces drop, use the

csnp-interval command in interface configuration mode to force periodic complete sequence number

PDUs (CSNPs) packets to be used on blocked point-to-point links. The use of periodic CSNPs enables

the network to become synchronized.

Mesh Group Configuration

Configuring mesh groups (a set of interfaces on a router) can help to limit flooding. All routers reachable

over the interfaces in a particular mesh group are assumed to be densely connected with each router

having at least one link to every other router. Many links can fail without isolating one or more routers

from the network.

In normal flooding, a new LSP is received on an interface and is flooded out over all other interfaces on

the router. With mesh groups, when a new LSP is received over an interface that is part of a mesh group,

the new LSP is not flooded over the other interfaces that are part of that mesh group.

Maximum LSP Lifetime and Refresh Interval

By default, the router sends a periodic LSP refresh every 15 minutes. LSPs remain in a database for

20 minutes by default. If they are not refreshed by that time, they are deleted. You can change the LSP

refresh interval or maximum LSP lifetime. The LSP interval should be less than the LSP lifetime or else

LSPs time out before they are refreshed. In the absence of a configured refresh interval, the software

adjusts the LSP refresh interval, if necessary, to prevent the LSPs from timing out.

Overload Bit Configuration During Multitopology Operation

Because the overload bit applies to forwarding for a single topology, it may be configured and cleared

independently for IPv4 and IPv6 during multitopology operation. For this reason, the overload is set

from the router address family configuration mode. If the IPv4 overload bit is set, all routers in the area

do not use the router for IPv4 transit traffic. However, they can still use the router for IPv6 transit traffic.

Single-Topology IPv6 Support

Single-topology IPv6 support on Cisco IOS XR software allows IS-IS for IPv6 to be configured on

interfaces along with an IPv4 network protocol. All interfaces must be configured with the identical set

of network protocols, and all routers in the IS-IS area (for Level 1 routing) or the domain (for Level 2

routing) must support the identical set of network layer protocols on all interfaces.

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Information About Implementing IS-IS on Cisco IOS XR Software

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Cisco IOS XR Routing Configuration Guide

When single-topology support for IPv6 is used, only narrow link metrics, also known as old-style type,

length, and value (TLV) arguments, may be employed. During single-topology operation, one shortest

path first (SPF) computation for each level is used to compute both IPv4 and IPv6 routes. Using a single

SPF is possible because both IPv4 IS-IS and IPv6 IS-IS routing protocols share a common link topology.

Because multitopology is the default behavior in the software, you must explicitly configure IPv6 to use

the same topology as IPv4 enable single-topology IPv6. Configure the single-topology command in

IPv6 router address family configuration submode of the IS-IS router stanza.

Multitopology IPv6 Support

Multitopology IPv6 support on Cisco IOS XR software for IS-IS assumes that multitopology support is

required as soon as it detects interfaces configured for both IPv6 and IPv4 within the IS-IS stanza.

Nonstop Forwarding

On Cisco IOS XR software, NSF minimizes the amount of time a network is unavailable to its users

following a route processor (RP) failover. The main objective of NSF is to continue forwarding IP

packets and perform a graceful restart following an RP failover.

When a router restarts, all routing peers of that device usually detect that the device went down and then

came back up. This transition results in what is called a routing flap, which could spread across multiple

routing domains. Routing flaps caused by routing restarts create routing instabilities, which are

detrimental to the overall network performance. NSF helps to suppress routing flaps in NSF-aware

devices, thus reducing network instability.

NSF allows for the forwarding of data packets to continue along known routes while the routing protocol

information is being restored following an RP failover. When the NSF feature is configured, peer

networking devices do not experience routing flaps. Data traffic is forwarded through intelligent line

cards or dual forwarding processors (FPs) while the standby RP assumes control from the failed active

RP during a failover. The ability of line cards and FPs to remain up through a failover and to be kept

current with the Forwarding Information Base (FIB) on the active RP is key to NSF operation.

When the Cisco IOS XR router running IS-IS routing performs an RP failover, the router must perform

two tasks to resynchronize its link-state database with its IS-IS neighbors. First, it must relearn the

available IS-IS neighbors on the network without causing a reset of the neighbor relationship. Second,

it must reacquire the contents of the link-state database for the network.

The IS-IS NSF feature offers two options when configuring NSF:

•IETF NSF

•Cisco NSF

If neighbor routers on a network segment are NSF aware, meaning that neighbor routers are running a

software version that supports the IETF Internet draft for router restartability, they assist an IETF NSF

router that is restarting. With IETF NSF, neighbor routers provide adjacency and link-state information

to help rebuild the routing information following a failover.

In Cisco IOS XR software, Cisco NSF checkpoints (stores persistently) all the state necessary to recover

from a restart without requiring any special cooperation from neighboring routers. The state is recovered

from the neighboring routers, but only using the standard features of the IS-IS routing protocol. This

capability makes Cisco NSF suitable for use in networks in which other routers have not used the IETF

standard implementation of NSF.

Implementing IS-IS on Cisco IOS XR Software

Information About Implementing IS-IS on Cisco IOS XR Software

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Cisco IOS XR Routing Configuration Guide

Note If you configure IETF NSF on the Cisco IOS XR router and a neighbor router does not support IETF

NSF, the affected adjacencies flap, but nonstop forwarding is maintained to all neighbors that do support

IETF NSF. A restart reverts to a cold start if no neighbors support IETF NSF.

Multi-Instance IS-IS

You may configure as many IS-IS instances as system resources (memory and interfaces) allow. Each

interface may be associated with only a single IS-IS instance, and MPLS may be enabled for only a

single IS-IS instance. Cisco IOS XR software prevents the double-booking of an interface by two

instances at configuration time—two instances of MPLS configuration causes an error.

Because the Routing Information Base (RIB) treats each of the IS-IS instances as equal routing clients,

you must be careful when redistributing routes between IS-IS instances. The RIB does not know to prefer

Level 1 routes over Level 2 routes. For this reason, if you are running Level 1 and Level 2 instances, you

must enforce the preference by configuring different administrative distances for the two instances.

Multiprotocol Label Switching Traffic Engineering

The MPLS TE feature enables an MPLS backbone to replicate and expand the traffic engineering

capabilities of Layer 2 ATM and Frame Relay networks. MPLS is an integration of Layer 2 and Layer 3

technologies.

For IS-IS, MPLS TE automatically establishes and maintains MPLS TE label-switched paths across the

backbone by using Resource Reservation Protocol (RSVP). The route that a label-switched path uses is

determined by the label-switched paths resource requirements and network resources, such as

bandwidth. Available resources are flooded by using special IS-IS TLV extensions in the IS-IS. The

label-switched paths are explicit routes and are referred to as traffic engineering (TE) tunnels.

Overload Bit on Router

The overload bit is a special bit of state information that is included in an LSP of the router. If the bit is

set on the router, it notifies routers in the area that the router is not available for transit traffic. This

capability is useful in four situations:

1. During a serious but nonfatal error, such as limited memory.

2. During the startup and restart of the process. The overload bit can be set until the routing protocol

has converged. However, it is not employed during a normal NSF restart or failover because doing

so causes a routing flap.

3. During a trial deployment of a new router. The overload bit can be set until deployment is verified,

then cleared.

4. During the shutdown of a router. The overload bit can be set to remove the router from the topology

before the router is removed from service.

Implementing IS-IS on Cisco IOS XR Software

Information About Implementing IS-IS on Cisco IOS XR Software

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Cisco IOS XR Routing Configuration Guide

Default Routes

You can force a default route into an IS-IS routing domain. Whenever you specifically configure

redistribution of routes into an IS-IS routing domain, the Cisco IOS XR software does not, by default,

redistribute the default route into the IS-IS routing domain. The default-information originate

command generates a default route into IS-IS, which can be controlled by a route map. You can use the

route map to identify the level into which the default route is to be announced, and you can specify other

filtering options configurable under a route map. You can use a route map to conditionally advertise the

default route, depending on the existence of another route in the routing table of the router.

Attached Bit on an IS-IS Instance

The attached bit is set in a router that is configured with the is-type command and level-1-2 keyword.

The attached bit indicates that the router is connected to other areas (typically through the backbone).

This functionality means that the router can be used by Level 1 routers in the area as the default route to

the backbone. The attached bit is usually set automatically as the router discovers other areas while

computing its Level 2 SPF route. The bit is automatically cleared when the router becomes detached

from the backbone. To simulate this behavior when using multiple processes to represent the level-1-2

keyword functionality, you would manually configure the attached bit on the Level 1 process.

Caution If the connectivity for the Level 2 instance is lost, the attached bit in the Level 1 instance LSP would

continue sending traffic to the Level 2 instance and cause the traffic to be dropped.

Multicast-Intact Feature

The multicast-intact feature provides the ability to run multicast routing (PIM) when IGP shortcuts are

configured and active on the router. Both OSPFv2 and IS-IS support the multicast-intact feature.

You can enable multicast-intact in the IGP when multicast routing protocols (PIM) are configured and

IGP shortcuts are configured on the router. IGP shortcuts are MPLS tunnels that are exposed to IGP. The

IGPs route the IP traffic over these tunnels to destinations that are downstream from the egress router of

the tunnel (from an SPF perspective). PIM cannot use IGP shortcuts for propagating PIM joins because

reverse path forwarding (RPF) cannot work across a unidirectional tunnel.

When you enable multicast-intact on an IGP, the IGP publishes a parallel or alternate set of equal-cost

next-hops for use by PIM. These next-hops are called mcast-intact next-hops. The mcast-intact

next-hops have the following attributes:

•They are guaranteed not to contain any IGP shortcuts.

•They are not used for unicast routing but are used only by PIM to look up an IPv4 next-hop to a PIM

source.

•They are not published to the FIB.

•When multicast-intact is enabled on an IGP, all IPv4 destinations that were learned through

link-state advertisements are published with a set equal-cost mcast-intact next-hops to the RIB. This

attribute applies even when the native next-hops have no IGP shortcuts.

•In IS-IS, the max-paths limit is applied by counting both the native and mcast-intact next-hops

together. (In OSPFv2, the behavior is slightly different.)

Implementing IS-IS on Cisco IOS XR Software

How to Implement IS-IS on Cisco IOS XR Software

RC-91

Cisco IOS XR Routing Configuration Guide

How to Implement IS-IS on Cisco IOS XR Software

This section contains the following procedures:

•Enabling IS-IS and Configuring Level 1 or Level 2 Routing, page RC-91 (required)

•Configuring Single Topology for IS-IS, page RC-93 (required)

•Configuring Multitopology for IS-IS, page RC-98 (optional)

•Controlling LSP Flooding for IS-IS, page RC-102 (optional)

•Configuring Nonstop Forwarding for IS-IS, page RC-106 (optional)

•Configuring Authentication for IS-IS, page RC-108 (optional)

•Configuring MPLS Traffic Engineering for IS-IS, page RC-110 (optional)

•Tuning Adjacencies for IS-IS on Point-to-Point Interfaces, page RC-113 (optional)

•Setting SPF Interval for a Single-Topology IPv4 and IPv6 Configuration, page RC-116 (optional)

•Enabling Multicast-Intact for IS-IS, page RC-118 (optional)

Note To save configuration changes, you must commit changes when the system prompts you.

Enabling IS-IS and Configuring Level 1 or Level 2 Routing

This task explains how to enable IS-IS and configure the routing level for an area.

Note Configuring the routing level in Step 4 is optional, but is highly recommended to establish the proper

level of adjacencies.

Prerequisites

Although you can configure IS-IS before you configure an IP address, no IS-IS routing occurs until at

least one IP address is configured.

SUMMARY STEPS

1. configure

2. router isis instance-id

3. net network-entity-title

4. is-type {level-1 | level-1-2 | level-2-only}

5. end

commit

6. show isis [instance instance-id] protocol

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Cisco IOS XR Routing Configuration Guide

DETAILED STEPS

Command or Action Purpose

Step 1 configure

Example:

RP/0/RP0/CPU0:router# configure

Enters global configuration mode.

Step 2 router isis

instance-id

Example:

RP/0/RP0/CPU0:router(config)# router isis isp

Enables IS-IS routing for the specified routing instance, and

places the router in router configuration mode.

•By default, all IS-IS instances are automatically

Level 1 and Level 2. You can change the level of

routing to be performed by a particular routing instance

using the is-type router configuration command.

Step 3 net

network-entity-title

Example:

RP/0/RP0/CPU0:router(config-isis)# net

47.0004.004d.0001.0001.0c11.1110.00

Configures network entity titles (NETs) for the routing

instance.

•Specify a NET for each routing instance if you are

configuring multi-instance IS-IS. You can specify a

name for a NET and for an address.

•This example configures a router with area ID

47.0004.004d.0001 and system ID 0001.0c11.1110.00.

•To specify more than one area address, specify

additional NETs. Although the area address portion of

the NET differs, the systemID portion of the NET must

match exactly for all of the configured items.

Step 4 is-type {level-1 | level-1-2 | level-2-only}

Example:

RP/0/RP0/CPU0:router(config-isis)# is-type

level-2-only

(Optional) Configures the system type (area or backbone

router).

•By default, every IS-IS instance acts as a level-1-2

router.

•The level-1 keyword configures the software to perform

Level 1 (intra-area) routing only. Only Level 1

adjacencies are established. The software learns about

destinations inside its area only. Any packets

containing destinations outside the area are sent to the

nearest level-1-2 router in the area.

•The level-2-only keyword configures the software to

perform Level 2 (backbone) routing only, and the router

establishes only Level 2 adjacencies, either with other

Level 2-only routers or with level-1-2 routers.

•The level-1-2 keyword configures the software to

perform both Level 1 and Level 2 routing. Both Level 1

and Level 2 adjacencies are established. The router acts

as a border router between the Level 2 backbone and its

Level 1 area.

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Cisco IOS XR Routing Configuration Guide

Configuring Single Topology for IS-IS

After an IS-IS instance is enabled, it must be configured to compute routes for a specific network

topology.

This task explains how to configure the operation of the IS-IS protocol on an interface for an IPv4 or

IPv6 topology.

Restrictions

To enable the router to run in single-topology mode, configure each of the IS-IS interfaces with all of

the address families enabled and “single-topology” in the address-family IPv6 unicast in the IS-IS router

stanza. You can use either the IPv6 address family or both IPv4 and IPv6 address families, but your

configuration must represent the set of all active address families on the router. In addition, you should

explicitly enable single-topology operation by configuring it in the IPv6 router address family submode.

Exceptions to these instructions exist:

1. If the address-family stanza in the IS-IS process contains the adjacency-check disable command,

then an interface is not required to have the address family enabled.

2. If the interface is configured to Level 2 only. (This exception permits the running of IPv4 and IPv6

areas.)

3. The single-topology command is not valid in the ipv4 address-family submode.

Step 5 end

commit

Example:

RP/0/RP0/CPU0:router(config-isis)# end

RP/0/RP0/CPU0:router(config-isis)# commit

Saves configuration changes.

•When you issue the end command, the system prompts

you to commit changes:

Uncommitted changes found, commit them before

exiting(yes/no/cancel)?

[cancel]:

–

Entering yes saves configuration changes to the

running configuration file, exits the configuration

session, and returns the router to EXEC mode.

–

Entering no exits the configuration session and

returns the router to EXEC mode without

committing the configuration changes.

–

Entering cancel leaves the router in the current

configuration session without exiting or

committing the configuration changes.

•Use the commit command to save the configuration

changes to the running configuration file and remain

within the configuration session.

Step 6 show isis [instance

instance-id

] protocol

Example:

RP/0/RP0/CPU0:router# show isis protocol

(Optional) Displays summary information about the IS-IS

instance.

Command or Action Purpose

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Cisco IOS XR Routing Configuration Guide

The default metric style for single topology is narrow metrics. However, you can use either wide metrics

or narrow metrics. How to configure them depends on how single topology is configured. If both IPv4

and IPv6 are enabled and single topology is configured, the metric style is configured in the

address-family ipv4 stanza. You may configure the metric style in the address-family ipv6 stanza, but

it is ignored in this case. If only IPv6 is enabled and single topology is configured, then the metric style

is configured in the address-family ipv6 stanza.

SUMMARY STEPS

1. configure

2. interface type number

3. ipv4 address address mask

ipv6 address ipv6-prefix/prefix-length [eui-64]

ipv6 address ipv6-address {/prefix-length | link-local}

ipv6 enable

4. exit

5. router isis instance-id

6. net network-entity-title

7. address-family ipv6 [unicast]

8. single-topology

9. exit

10. interface type instance

11. circuit-type {level-1 | level-1-2 | level-2-only}

12. address-family {ipv4 | ipv6} [unicast]

13. end

commit

14. show isis [instance instance-id] interface [type instance] [detail] [level {1 | 2}]

15. show isis [instance instance-id] topology [systemid system-id] [level {1 | 2}] [summary]

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Cisco IOS XR Routing Configuration Guide

DETAILED STEPS

Command or Action Purpose

Step 1 configure

Example:

RP/0/RP0/CPU0:router# configure

Enters global configuration mode.

Step 2 interface

type number

Example:

RP/0/RP0/CPU0:router(config)# interface POS

0/1/0/3

Enters interface configuration mode.

Step 3 ipv4 address

address mask

ipv6 address

ipv6-prefix

prefix-length

[eui-64]

ipv6 address

ipv6-address

prefix-length

link-local

}

ipv6 enable

Example:

RP/0/RP0/CPU0:router(config-if)# ipv4 address

10.0.1.3 255.255.255.0

RP/0/RP0/CPU0:router(config-if)# ipv6 address

3ffe:1234:c18:1::/64 eui-64

RP/0/RP0/CPU0:router(config-if)# ipv6 address

FE80::260:3EFF:FE11:6770 link-local

RP/0/RP0/CPU0:router(config-if)# ipv6 enable

Defines the IPv4 address for the interface. An IP address is

required on all interfaces in an area enabled for IS-IS if any

one interface is configured for IS-IS routing.

Specifies an IPv6 network assigned to the interface and

enables IPv6 processing on the interface with the eui-64

keyword.

Specifies an IPv6 address assigned to the interface and

enables IPv6 processing on the interface with the link-local

keyword.

Automatically configures an IPv6 link-local address on the

interface while also enabling the interface for IPv6

processing.

•The link-local address can be used only to

communicate with nodes on the same link.

•Specifying the ipv6 address ipv6-prefix/prefix-length

interface configuration command without the eui-64

keyword configures site-local and global IPv6

addresses.

•Specifying the ipv6 address ipv6-prefix/prefix-length

command with the eui-64 keyword configures

site-local and global IPv6 addresses with an interface

ID in the low-order 64 bits of the IPv6 address. Only the

64-bit network prefix for the address needs to be

specified; the last 64 bits are automatically computed

from the interface ID.

•Specifying the ipv6 address command with the

link-local keyword configures a link-local address on

the interface that is used instead of the link-local

address that is automatically configured when IPv6 is

enabled on the interface.

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Step 4 exit

Example:

RP/0/RP0/CPU0:router(config-if)# exit

Exits interface configuration mode, and returns the router to

global configuration mode.

Step 5 router isis

instance-id

Example:

RP/0/RP0/CPU0:router(config)# router isis isp

Enables IS-IS routing for the specified routing instance, and

places the router in router configuration mode.

•By default, all IS-IS instances are Level 1 and Level 2.

You can change the level of routing to be performed by

a particular routing instance using the is-type

command.

Step 6 net

network-entity-title

Example:

RP/0/RP0/CPU0:router(config-isis)# net

47.0004.004d.0001.0001.0c11.1110.00

Configures NETs for the routing instance.

•Specify a NET for each routing instance if you are

configuring multi-instance IS-IS. You can specify a

name for a NET and for an address.

•This example configures a router with area ID

47.0004.004d.0001 and system ID 0001.0c11.1110.00.

•To specify more than one area address, specify

additional NETs. Although the area address portion of

the NET differs, the system ID portion of the NET must

match exactly for all of the configured items.

Step 7 address-family ipv6 [unicast]

Example:

RP/0/RP0/CPU0:router(config-isis)#

address-family ipv6 unicast

Specifies the IPv6 address family and enters router address

family configuration mode.

•This example specifies the unicast IPv6 address family.

Step 8 single-topology

Example:

RP0/0/RP0/CPU0:router(config-isis-af)#

single-topology

(Optional) Configures the link topology for IPv4 when IPv6

is configured.

•The single-topology command is valid only in IPv6

submode. The command instructs IPv6 to use the single

topology rather than the default configuration of a

separate topology in the multitopology mode.

•See the “Single-Topology IPv6 Support” section on

page RC-87 for more information.

Step 9 exit

Example:

RP/0/RP0/CPU0:router(config-isis-af)# exit

Exits router address family configuration mode, and returns

the router to router configuration mode.

Step 10 interface

type instance

Example:

RP/0/RP0/CPU0:router(config-isis)# interface

POS 0/1/0/3

Enters interface configuration mode.

Command or Action Purpose

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Step 11 circuit-type {level-1 | level-1-2 |

level-2-only}

Example:

RP/0/RP0/CPU0:router(config-isis-if)#

circuit-type level-1-2

(Optional) Configures the type of adjacency.

•The default circuit type is the configured system type

(configured through the is-type command).

•Typically, the circuit type must be configured when the

router is configured as only level-1-2 and you want to

constrain an interface to form only level-1 or

level-2-only adjacencies.

Step 12 address-family {ipv4 | ipv6} [unicast]

Example:

RP/0/RP0/CPU0:router(config-isis-if)#

address-family ipv6 unicast

Specifies the IPv4 or IPv6 address family, and enters

interface address family configuration mode.

•This example specifies the unicast IPv6 address family

on the interface.

Step 13 end

commit

Example:

RP/0/RP0/CPU0:router(config-isis-af)# end

RP/0/RP0/CPU0:router(config-isis-af)# commit

Saves configuration changes.

•When you issue the end command, the system prompts

you to commit changes:

Uncommitted changes found, commit them before

exiting(yes/no/cancel)?

[cancel]:

–

Entering yes saves configuration changes to the

running configuration file, exits the configuration

session, and returns the router to EXEC mode.

–

Entering no exits the configuration session and

returns the router to EXEC mode without

committing the configuration changes.

–

Entering cancel leaves the router in the current

configuration session without exiting or

committing the configuration changes.

•Use the commit command to save the configuration

changes to the running configuration file and remain

within the configuration session.

Step 14 show isis [instance

instance-id

] interface

[

type

instance

] [detail] [level {1 | 2}]

Example:

RP/0/RP0/CPU0:router# show isis interface

POS0/1/0/1

(Optional) Displays information about the IS-IS interface.

Step 15 show isis [instance

instance-id

] topology

[systemid

system-id

] [level {1 | 2}] [summary]

Example:

RP/0/RP0/CPU0:router# show isis topology

(Optional) Displays a list of connected routers in all areas.

Command or Action Purpose

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Configuring Multitopology for IS-IS

This task explains how to configure multitopology IS-IS. This task is optional. Multitopology is

configured in much the same way as the single topology for IPv4 and IPv6 address families. The single-

topology command is omitted, invoking the default multitopology behavior.

SUMMARY STEPS

1. configure

2. interface type instance

3. ipv4 address address mask

ipv6 address ipv6-prefix/prefix-length [eui-64]

ipv6 address ipv6-address {/prefix-length | link-local}

ipv6 enable

4. exit

5. router isis instance-id

6. net network-entity-title

7. interface type instance

8. address-family ipv4 [unicast]

9. exit

10. address-family ipv6 [unicast]

11. end

commit

12. show isis [instance instance-id] interface [type number] [brief | detail] [level {1 | 2}]

13. show isis [instance instance-id] topology [systemid system-id] [level {1 | 2}] [ipv4 | ipv6]

[summary] [unicast]

14. show isis [instance instance-id] adjacency [level {1 | 2}] [interface-type interface-instance]

[detail] [systemid system-id]

15. show isis adjacency-log [level {1 | 2}]

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DETAILED STEPS

Command or Action Purpose

Step 1 configure

Example:

RP/0/RP0/CPU0:router# configure

Enters global configuration mode.

Step 2 interface

type instance

Example:

RP/0/RP0/CPU0:router(config)# interface POS

0/1/0/3

Enters interface configuration mode.

Step 3 ipv4 address

address mask

ipv6 address

ipv6-prefix

prefix-length

[eui-64]

ipv6 address

ipv6-address

prefix-length

link-local

}

ipv6 enable

Example:

RP/0/RP0/CPU0:router(config-if)# ipv4 address

10.0.1.3 255.255.255.0

RP/0/RP0/CPU0:router(config-if)# ipv6 address

3ffe:1234:c18:1::/64 eui-64

RP/0/RP0/CPU0:router(config-if)# ipv6 address

FE80::260:3EFF:FE11:6770 link-local

RP/0/RP0/CPU0:router(config-if)# ipv6 enable

Defines the IPv4 address for the interface.

•An IP address is required on all interfaces in an area

enabled for IS-IS if any one interface is configured for

IS-IS routing.

Specifies an IPv6 network assigned to the interface and

enables IPv6 processing on the interface.

Specifies an IPv6 address assigned to the interface and

enables IPv6 processing on the interface.

Automatically configures an IPv6 link-local address on the

interface while also enabling the interface for IPv6

processing.

•The link-local address can be used to communicate

only with nodes on the same link.

•Specifying the ipv6 address ipv6-prefix/prefix-length

interface configuration command without the eui-64

keyword configures site-local and global IPv6

addresses.

•Specifying the ipv6 address ipv6-prefix/prefix-length

command with the eui-64 keyword configures

site-local and global IPv6 addresses with an interface

ID in the low-order 64 bits of the IPv6 address. Only the

64-bit network prefix for the address needs to be

specified; the last 64 bits are automatically computed

from the interface ID.

•Specifying the ipv6 address command with the

link-local keyword configures a link-local address on

the interface that is used instead of the link-local

address that is automatically configured when IPv6 is

enabled on the interface.

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Step 4 exit

Example:

RP/0/RP0/CPU0:router(config-if)# exit

Exits interface configuration mode, and returns the router to

global configuration mode.

Step 5 router isis

instance-id

Example:

RP/0/RP0/CPU0:router(config)# router isis isp

Enables IS-IS routing for the specified routing instance, and

places the router in router configuration mode.

•You can change the level of routing to be performed by

a particular routing instance using the is-type router

configuration command.

Step 6 net

network-entity-title

Example:

RP/0/RP0/CPU0:router(config-isis)# net

47.0004.004d.0001.0001.0c11.1110.00

Configures NETs for the routing instance.

•Specify a NET for each routing instance if you are

configuring multi-instance IS-IS. You can specify a

name for a NET and for an address.

•This example configures a router with area ID

47.0004.004d.0001 and system ID 0001.0c11.1110.10.

•To specify more than one area address, specify

additional NETs. Although the area address portion of

the NET differs, the system ID portion of the NET must

match exactly for all of the configured items.

Step 7 interface

type instance

Example:

RP/0/RP0/CPU0:router(config-isis)# interface

POS 0/1/0/4

Enters interface configuration mode.

Step 8 address-family ipv4 [unicast]

Example:

RP/0/RP0/CPU0:router(config-isis-if)#

address-family ipv4 unicast

Specifies the IPv4 address family and enters interface

address family configuration mode.

•This example specifies the unicast IPv4 address family.

Step 9 exit

Example:

RP/0/RP0/CPU0:router(config-if)# exit

Exits interface configuration mode, and returns the router to

interface configuration mode.

Step 10 address-family ipv6 [unicast]

Example:

RP/0/RP0/CPU0:router(config-isis-if)#

address-family ipv6 unicast

Specifies the IPv6 address family and enters interface

address family configuration mode.

•This example specifies the unicast IPv6 address family.

Command or Action Purpose

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Step 11 end

commit

Example:

RP/0/RP0/CPU0:router(config-isis-if-af)# end

RP/0/RP0/CPU0:router(config-isis-if-af)# commit

Saves configuration changes.

•When you issue the end command, the system prompts

you to commit changes:

Uncommitted changes found, commit them before

exiting(yes/no/cancel)?

[cancel]:

–

Entering yes saves configuration changes to the

running configuration file, exits the configuration

session, and returns the router to EXEC mode.

–

Entering no exits the configuration session and

returns the router to EXEC mode without

committing the configuration changes.

–

Entering cancel leaves the router in the current

configuration session without exiting or

committing the configuration changes.

•Use the commit command to save the configuration

changes to the running configuration file and remain

within the configuration session.

Step 12 show isis [instance

instance-id

] interface

[

type

instance

] [brief | detail] [level {1 |

2}]

Example:

RP/0/RP0/CPU0:router# show isis interface POS

0/1/0/1 brief

(Optional) Displays information about the IS-IS interface.

Step 13 show isis [instance

instance-id

] topology

[systemid

system-id

] [level {1 | 2}] [ipv4 |

ipv6] [summary] [unicast]

Example:

RP/0/RP0/CPU0:router# show isis topology

(Optional) Displays a list of connected routers in all areas.

Step 14 show isis [instance

instance-id

] adjacency

[level {1 | 2}] [

interface-type

interface-instance

] [

detail

] [systemid

system-id

]

Example::

RP/0/RP0/CPU0:router# show isis adjacency

(Optional) Displays state information about established

adjacencies.

Step 15 show isis adjacency-log [level {1 | 2}]

Example:

RP/0/RP0/CPU0:router# show isis adjacency-log

level 1

(Optional) Displays the history of recent adjacency state

transitions.

Command or Action Purpose

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Controlling LSP Flooding for IS-IS

Flooding of LSPs can limit network scalability. You can control LSP flooding by tuning your LSP

database parameters on the router globally or on the interface. This task is optional.

Many of the commands to control LSP flooding contain an option to specify the level to which they

apply. Without the option, the command applies to both levels. If an option is configured for one level,

the other level continues to use the default value. To configure options for both levels, use the command

twice. For example:

RP/0/RP0/CPU0:router(config-isis)# lsp-refresh-interval 1200 level 2

RP/0/RP0/CPU0:router(config-isis)# lsp-refresh-interval 1100 level 1

SUMMARY STEPS

1. configure

2. router isis instance-id

3. lsp-refresh-interval seconds [level {1 | 2}]

4. lsp-check-interval seconds [level {1 | 2}]

5. lsp-gen-interval {[initial-wait initial | secondary-wait secondary | maximum-wait maximum]

...}[level {1 | 2}]

6. lsp-mtu bytes [level {1 | 2}]

7. max-lsp-lifetime seconds [level {1 | 2}]

8. ignore-lsp-errors disable

9. interface type instance

10. lsp-interval milliseconds [level {1 | 2}]

11. csnp-interval seconds [level {1 | 2}]

12. retransmit-interval seconds [level {1 | 2}]

13. retransmit-throttle-interval milliseconds [level {1 | 2}]

14. mesh-group {number | blocked}

15. end

commit

16. show isis interface [type instance | level {1 | 2}] [brief]

17. show isis [instance instance-id] database [level {1 | 2}] [detail | summary | verbose] [* | lsp-id]

18. show isis [instance instance-id] lsp-log [level {1 | 2}]

19. show isis database-log [level {1 | 2}]

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DETAILED STEPS

Command or Action Purpose

Step 1 configure

Example:

RP/0/RP0/CPU0:router# configure

Enters global configuration mode.

Step 2 router isis

instance-id

Example:

RP/0/RP0/CPU0:router(config)# router isis isp

Enables IS-IS routing for the specified routing instance, and

places the router in router configuration mode.

•You can change the level of routing to be performed by

a particular routing instance using the is-type router

configuration command.

Step 3 lsp-refresh-interval

seconds

[level {1 | 2}]

Example:

RP/0/RP0/CPU0:router(config-isis)#

lsp-refresh-interval 10800

(Optional) Sets the time between regeneration of LSPs that

contain different sequence numbers

•The refresh interval should always be set lower than the

max-lsp-lifetime command.

Step 4 lsp-check-interval

seconds

[level {1 | 2}]

Example:

RP/0/RP0/CPU0:router(config-isis)#

lsp-check-interval 240

(Optional) Configures the time between periodic checks of

the entire database to validate the checksums of the LSPs in

the database.

•This operation is costly in terms of CPU and so should

be configured to occur infrequently.

Step 5 lsp-gen-interval {[initial-wait

initial

secondary-wait

secondary

| maximum-wait

maximum

] ...}[level {1 | 2}]

Example:

RP/0/RP0/CPU0:router(config-isis)#

lsp-gen-interval maximum-wait 15 initial-wait 5

(Optional) Reduces the rate of LSP generation during

periods of instability in the network. Helps reduce the CPU

load on the router and number of LSP transmissions to its

IS-IS neighbors.

•During prolonged periods of network instability,

repeated recalculation of LSPs can cause an increased

CPU load on the local router. Further, the flooding of

these recalculated LSPs to the other Intermediate

Systems in the network causes increased traffic and can

result in other routers having to spend more time

running route calculations.

Step 6 lsp-mtu

bytes

[level {1 | 2}]

Example:

RP/0/RP0/CPU0:router(config-isis)# lsp-mtu 1300

(Optional) Sets the maximum transmission unit (MTU) size

of LSPs.

Step 7 max-lsp-lifetime

seconds

[level {1 | 2}]

Example:

RP/0/RP0/CPU0:router(config-isis)#

max-lsp-lifetime 11000

(Optional) Sets the initial lifetime given to an LSP

originated by the router.

•This is the amount of time that the LSP persists in the

database of a neighbor unless the LSP is regenerated or

refreshed.

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Step 8 ignore-lsp-errors disable

Example:

RP/0/RP0/CPU0:router(config-isis)#

ignore-lsp-errors disable

(Optional) Sets the router to purge LSPs received with

checksum errors.

Step 9 interface

type instance

Example:

RP/0/RP0/CPU0:router(config-isis)# interface

POS 0/1/0/3

Enters interface configuration mode.

Step 10 lsp-interval

milliseconds

[level {1 | 2}]

Example:

RP/0/RP0/CPU0:router(config-isis-if)#

lsp-interval 100

(Optional) Configures the amount of time between each

LSP sent on an interface.

Step 11 csnp-interval

seconds

[level {1 | 2}]

Example:

RP/0/RP0/CPU0:router(config-isis-if)#

csnp-interval 30 level 1

(Optional) Configures the interval at which periodic CSNP

packets are sent on broadcast interfaces.

•Sending more frequent CSNPs means that adjacent

routers must work harder to receive them.

•Sending less frequent CSNP means that differences in

the adjacent routers may persist longer.

Step 12 retransmit-interval

seconds

[level {1 | 2}]

Example:

RP/0/RP0/CPU0:router(config-isis-if)#

retransmit-interval 60

(Optional) Configures the amount of time that the sending

router waits for an acknowledgment before it considers that

the LSP was not received and subsequently resends.

Step 13 retransmit-throttle-interval

milliseconds

[level {1 | 2}]

Example:

RP/0/RP0/CPU0:router(config-isis-if)#

retransmit-throttle-interval 1000

(Optional) Configures the amount of time between

retransmissions on each LSP on a point-to-point interface.

•This time is usually greater than or equal to the

lsp-interval command time because the reason for lost

LSPs may be that a neighboring router is busy. A longer

interval gives the neighbor more time to receive

transmissions.

Step 14 mesh-group {

number

| blocked}

Example:

RP/0/RP0/CPU0:router(config-isis-if)#

mesh-group blocked

(Optional) Optimizes LSP flooding in NBMA networks

with highly meshed, point-to-point topologies.

•This command is appropriate only for an NBMA

network with highly meshed, point-to-point topologies.

Command or Action Purpose

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Step 15 end

commit

Example:

RP/0/RP0/CPU0:router(config-isis-if)# end

RP/0/RP0/CPU0:router(config-isis-if)# commit

Saves configuration changes.

•When you issue the end command, the system prompts

you to commit changes:

Uncommitted changes found, commit them before

exiting(yes/no/cancel)?

[cancel]:

–

Entering yes saves configuration changes to the

running configuration file, exits the configuration

session, and returns the router to EXEC mode.

–

Entering no exits the configuration session and

returns the router to EXEC mode without

committing the configuration changes.

–

Entering cancel leaves the router in the current

configuration session without exiting or

committing the configuration changes.

•Use the commit command to save the configuration

changes to the running configuration file and remain

within the configuration session.

Step 16 show isis interface [

type

instance

| level {1 |

2}] [brief]

Example:

RP/0/RP0/CPU0:router# show isis interface

POS0/1/0/1 brief

(Optional) Displays information about the IS-IS interface.

Step 17 show isis [instance

instance-id

] database

[level {1 | 2}] [detail | summary | verbose] [*

lsp-id

]

Example:

RP/0/RP0/CPU0:router# show isis database

level 1

(Optional) Displays the IS-IS LSP database.

Step 18 show isis [instance

instance-id

] lsp-log [level

{1 | 2}]

Example:

RP/0/RP0/CPU0:router# show isis lsp-log

(Optional) Displays LSP log information.

Step 19 show isis database-log [level {1 | 2}]

Example:

RP/0/RP0/CPU0:router# show isis database-log

level 1

(Optional) Display IS-IS database log information.

Command or Action Purpose

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Configuring Nonstop Forwarding for IS-IS

This task explains how to configure your router with NSF that allows the Cisco IOS XR software to

resynchronize the IS-IS link-state database with its IS-IS neighbors after a process restart. The process

restart could be due to an:

•RP failover (for a warm restart)

•Simple process restart (due to an IS-IS reload or other administrative request to restart the process)

•IS-IS software upgrade

In all cases, NSF mitigates link flaps and loss of user sessions. This task is optional.

SUMMARY STEPS

1. configure

2. router isis instance-id

3. nsf {cisco | ietf}

4. nsf interface-expires number

5. nsf interface-timer seconds

6. nsf lifetime seconds

7. end

commit

8. show running-config [command]

DETAILED STEPS

Command or Action Purpose

Step 1 configure

Example:

RP/0/RP0/CPU0:router# configure

Enters global configuration mode.

Step 2 router isis

instance-id

Example:

RP/0/RP0/CPU0:router(config)# router isis isp

Enables IS-IS routing for the specified routing instance, and

places the router in router configuration mode.

•You can change the level of routing to be performed by

a particular routing instance using the is-type router

configuration command.

Step 3 nsf {cisco | ietf}

Example:

RP/0/RP0/CPU0:router(config-isis)# nsf ietf

Enables NSF on the next restart.

•Enter the cisco keyword to run IS-IS in heterogeneous

networks that might not have adjacent NSF-aware

networking devices.

•Enter the ietf keyword to enable IS-IS in homogeneous

networks where all adjacent networking devices

support IETF draft-based restartability.

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Step 4 nsf interface-expires

number

Example:

RP/0/RP0/CPU0:router(config-isis)# nsf

interface-expires 1

Configures the number of resends of an acknowledged

NSF-restart acknowledgment.

•If the resend limit is reached during the NSF restart, the

restart falls back to a cold restart.

Step 5 nsf interface-timer

seconds

Example:

RP/0/RP0/CPU0:router(config-isis) nsf

interface-timer 15

Configures the number of seconds to wait for each restart

acknowledgment.

Step 6 nsf lifetime

seconds

Example:

RP/0/RP0/CPU0:router(config-isis)# nsf lifetime

Configures the maximum route lifetime following an NSF

restart.

•This command should be configured to the length of

time required to perform a full NSF restart because it is

the amount of time that the Routing Information Base

(RIB) retains the routes during the restart.

•Setting this value too high results in stale routes.

•Setting this value too low could result in routes purged

too soon.

Step 7 end

commit

Example:

RP/0/RP0/CPU0:router(config-isis)# end

RP/0/RP0/CPU0:router(config-isis)# commit

Saves configuration changes.

•When you issue the end command, the system prompts

you to commit changes:

Uncommitted changes found, commit them before

exiting(yes/no/cancel)?

[cancel]:

–

Entering yes saves configuration changes to the

running configuration file, exits the configuration

session, and returns the router to EXEC mode.

–

Entering no exits the configuration session and

returns the router to EXEC mode without

committing the configuration changes.

–

Entering cancel leaves the router in the current

configuration session without exiting or

committing the configuration changes.

•Use the commit command to save the configuration

changes to the running configuration file and remain

within the configuration session.

Step 8 show running-config [

command

]

Example:

RP/0/RP0/CPU0:router# show running-config

router isis isp

(Optional) Displays the entire contents of the currently

running configuration file or a subset of that file.

•Verify that “nsf” appears in the IS-IS configuration of

the NSF-aware device.

•This example shows the contents of the configuration

file for the “isp” instance only.

Command or Action Purpose

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Cisco IOS XR Routing Configuration Guide

Configuring Authentication for IS-IS

This task explains how to configure authentication for IS-IS. This task is optional.

Authentication is available to limit the establishment of adjacencies by using the hello-password

configuration, and to limit the exchange of LSPs by using the LSP password.

IS-IS supports plain-text authentication, which does not provide security against hackers or other

unauthorized users. Plain-text authentication allows you to configure a password to prevent unauthorized

networking devices from forming adjacencies with this router. The password is exchanged as plain text

and is potentially visible to an agent able to view the IS-IS packets.

IS-IS stores a configured password using simple encryption. However, the plain-text form of the

password is used in LSPs, sequence number protocols (SNPs), and hello packets, which would be visible

to a process that can view IS-IS packets. The passwords can be entered in plain text (preceded by a 0) or

encrypted (preceded by a 7) form.

To set the domain password, configure the lsp-password for Level 2; to set the area password, configure

the lsp-password for Level 1.

SUMMARY STEPS

1. configure

2. router isis instance-id

3. lsp-password {hmac-md5 | text} {clear | encrypted} password [level {1 | 2}] [send-only] [snp

send-only]

4. interface type instance

5. hello-password {hmac-md5 | text} {clear | encrypted} password [level {1 | 2}] [send-only]

6. end

commit

DETAILED STEPS

Command or Action Purpose

Step 1 configure

Example:

RP/0/RP0/CPU0:router# configure

Enters global configuration mode.

Step 2 router isis

instance-id

Example:

RP/0/RP0/CPU0:router(config)# router isis isp

Enables IS-IS routing for the specified routing instance, and

places the router in router configuration mode.

•You can change the level of routing to be performed by

a particular routing instance using the is-type

command.

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Step 3 lsp-password {hmac-md5 | text} {clear |

encrypted}

password

[level {1 | 2}] [send-only]

[snp send-only]

Example:

RP/0/RP0/CPU0:router(config-isis)# lsp-password

hmac-md5 encrypted password1 level 1

Configures the LSP authentication password.

•The hmac-md5 keyword specifies that the password is

used in HMAC-MD5 authentication.

•The text keyword specifies that the password uses

cleartext password authentication.

•The clear keyword specifies that the password is

unencrypted when entered.

•The encrypted keyword specifies that the password is

encrypted using a two-way algorithm when entered.

•The level 1 keyword sets a password for authentication

in the area (in Level 1 LSPs and Level SNPs).

•The level 2 keywords set a password for authentication

in the backbone (the Level 2 area).

•The send-only keyword adds authentication to LSP and

sequence number protocol data units (SNPs) when they

are sent. It does not authenticate received LSPs or

SNPs.

•The snp send-only keyword adds authentication to

SNPs when they are sent. It does not authenticate

received SNPs.

Note To disable SNP password checking, the snp

send-only keywords must be specified in the

lsp-password command.

Step 4 interface

type instance

Example:

RP/0/RP0/CPU0:router(config-isis)# interface

POS 0/1/0/3

Enters interface configuration mode.

Command or Action Purpose

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Cisco IOS XR Routing Configuration Guide

Configuring MPLS Traffic Engineering for IS-IS

This task explains how to configure IS-IS for MPLS TE. This task is optional.

For a description of the MPLS TE tasks and commands that allow you to configure the router to support

tunnels, configure an MPLS tunnel that IS-IS can use, and troubleshoot MPLS TE, see the Implementing

MPLS Traffic Engineering on Cisco IOS XR Software.

Prerequisite

Your network must support the following Cisco IOS XR software features before you enable MPLS TE

for IS-IS on your router:

•MPLS

•IP Cisco Express Forwarding (CEF)

Note You must enter the commands in the following task list on every IS-IS router in the traffic-engineered

portion of your network.

Step 5 hello-password {hmac-md5 | text} {clear |

encrypted}

password

[level {1 | 2}] [send-only]

Example:

RP/0/RP0/CPU1:router(config-isis-if)#

hello-password text clear mypassword

Configures the authentication password for an IS-IS

interface.

Step 6 end

commit

Example:

RP/0/RP0/CPU0:router(config-isis-if)# end

RP/0/RP0/CPU0:router(config-isis-if)# commit

Saves configuration changes.

•When you issue the end command, the system prompts

you to commit changes:

Uncommitted changes found, commit them before

exiting(yes/no/cancel)?

[cancel]:

–

Entering yes saves configuration changes to the

running configuration file, exits the configuration

session, and returns the router to EXEC mode.

–

Entering no exits the configuration session and

returns the router to EXEC mode without

committing the configuration changes.

–

Entering cancel leaves the router in the current

configuration session without exiting or

committing the configuration changes.

•Use the commit command to save the configuration

changes to the running configuration file and remain

within the configuration session.

Command or Action Purpose

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Cisco IOS XR Routing Configuration Guide

Restrictions

MPLS traffic engineering currently supports only a single IS-IS level and does not support routing and

signaling of LSPs over unnumbered IP links. Therefore, do not configure the feature over those links.

SUMMARY STEPS

1. configure

2. router isis instance-id

3. address-family {ipv4 | ipv6} [unicast]

4. mpls traffic-eng level {1 | 2}

5. mpls traffic-eng router-id {ip-address | interface-name}

6. metric-style wide [level {1 | 2}]

7. end

commit

8. show isis [instance instance-id] mpls traffic-eng tunnel

9. show isis [instance instance-id] mpls traffic-eng adjacency-log

10. show isis [instance instance-id] mpls traffic-eng advertisements

DETAILED STEPS

Command or Action Purpose

Step 1 configure

Example:

RP/0/RP0/CPU0:router# configure

Enters global configuration mode.

Step 2 router isis

instance-id

Example:

RP/0/RP0/CPU0:router(config)# router isis isp

Enables IS-IS routing for the specified routing instance, and

places the router in router configuration mode.

•You can change the level of routing to be performed by

a particular routing instance using the is-type router

configuration command.

Step 3 address-family {ipv4 | ipv6} [unicast]

Example:

RP/0/RP0/CPU0:router(config-isis)#

address-family ipv6 unicast

Specifies the IPv4 or IPv6 address family, and enters router

address family configuration mode.

•This example specifies the unicast IPv6 address family.

Step 4 mpls traffic-eng level {1 | 2}

Example:

RP/0/RP0/CPU0:router(config-isis-af)# mpls

traffic-eng level 1

Configures a router running IS-IS to flood MPLS TE link

information into the indicated IS-IS level.

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Step 5 mpls traffic-eng router-id {

ip-address

interface-name

}

Example:

RP/0/RP0/CPU0:router(config-isis-af)# mpls

traffic-eng router-id loopback0

Specifies that the MPLS TE router identifier for the node is

the IP address and or name associated with a given

interface.

Step 6 metric-style wide [level {1 | 2}]

Example:

RP/0/RP0/CPU0:router(config-isis-af)#

metric-style wide level 1

Configures a router to generate and accept only wide link

metrics in the Level 1 area.

Step 7 end

commit

Example:

RP/0/RP0/CPU0:router(config-isis-af)# end

RP/0/RP0/CPU0:router(config-isis-af)# commit

Saves configuration changes.

•When you issue the end command, the system prompts

you to commit changes:

Uncommitted changes found, commit them before

exiting(yes/no/cancel)?

[cancel]:

–

Entering yes saves configuration changes to the

running configuration file, exits the configuration

session, and returns the router to EXEC mode.

–

Entering no exits the configuration session and

returns the router to EXEC mode without

committing the configuration changes.

–

Entering cancel leaves the router in the current

configuration session without exiting or

committing the configuration changes.

•Use the commit command to save the configuration

changes to the running configuration file and remain

within the configuration session.

Step 8 show isis [instance

instance-id

] mpls

traffic-eng tunnel

Example:

RP/0/RP0/CPU0:router# show isis instance isp

mpls traffic-eng tunnel

(Optional) Displays MPLS TE tunnel information.

Step 9 show isis [instance

instance-id

] mpls

traffic-eng adjacency-log

Example:

RP/0/RP0/CPU0:router# show isis instance isp

mpls traffic-eng adjacency-log

(Optional) Displays a log of MPLS TE IS-IS adjacency

changes.

Step 10 show isis [instance

instance-id

] mpls

traffic-eng advertisements

Example:

RP/0/RP0/CPU0:router# show isis instance isp

mpls traffic-eng advertisements

(Optional) Displays the latest flooded record from MPLS

TE.

Command or Action Purpose

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Cisco IOS XR Routing Configuration Guide

Tuning Adjacencies for IS-IS on Point-to-Point Interfaces

This task explains how to enable logging of adjacency state changes, alter the timers for IS-IS adjacency

packets, and display various aspects of adjacency state. Tuning your IS-IS adjacencies increases network

stability when links are congested. This task is optional.

For point-to-point links, IS-IS sends only a single hello for Level 1 and Level 2, which means that the

level modifiers are meaningless on point-to-point links. To modify hello parameters for a point-to-point

interface, omit the specification of the level options.

The options configurable in the interface submode apply only to that interface. By default, the values are

applied to both Level 1 and Level 2.

The hello-password command can be used to prevent adjacency formation with unauthorized or

undesired routers. This ability is particularly useful on a LAN, where connections to routers with which

you have no desire to establish adjacencies are commonly found.

SUMMARY STEPS

1. configure

2. router isis instance-id

3. log adjacency changes

4. interface type number

5. hello-padding {disable | sometimes} [level {1 | 2}]

6. hello-interval seconds [level {1 | 2}]

7. hello-multiplier multiplier [level {1 | 2}]

8. hello-password {hmac-md5 | text} {clear | encrypted} password [level {1 | 2}] [send-only]

9. end

commit

10. show isis [instance instance-id] adjacency [interface-type interface-instance] [detail] [systemid

system-id]

11. show isis adjacency-log

12. show isis [instance instance-id] interface [type instance] [brief | detail] [level {1 | 2}]

13. show isis [instance instance-id] neighbors [interface-type interface-instance] [summary] [detail]

[systemid system-id]

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DETAILED STEPS

Command or Action Purpose

Step 1 configure

Example:

RP/0/RP0/CPU0:router# configure

Enters global configuration mode.

Step 2 router isis

instance-id

Example:

RP/0/RP0/CPU0:router(config)# router isis isp

Enables IS-IS routing for the specified routing instance,

and places the router in router configuration mode.

•You can change the level of routing to be performed

by a particular routing instance using the is-type

command.

Step 3 log adjacency changes

Example:

RP/0/RP0/CPU0:router(config-isis)# log adjacency

changes

Generates a log message when an IS-IS adjacency

changes state (up or down).

Step 4 interface

type number

Example:

RP/0/RP0/CPU0:router(config-isis)# interface POS

0/1/0/3

Enters interface configuration mode.

Step 5 hello-padding {disable | sometimes} [level {1 |

2}]

Example:

RP/0/RP0/CPU0:router(config-isis-if)# hello-paddi

ng sometimes

Configures padding on IS-IS hello PDUs for all IS-IS

interfaces on the router.

•Hello padding applies to only this interface and not

to all interfaces.

Step 6 hello-interval

seconds

[level {1 | 2}]

Example:

RP/0/RP0/CPU0:router(config-isis-if)#

hello-interval 6

Specifies the length of time between hello packets that

the software sends.

Step 7 hello-multiplier

multiplier

[level {1 | 2}]

Example:

RP/0/RP0/CPU0:router(config-isis-if)#

hello-multiplier 10

Specifies the number of IS-IS hello packets a neighbor

must miss before the router should declare the adjacency

as down.

•A higher value increases the networks tolerance for

dropped packets, but also may increase the amount

of time required to detect the failure of an adjacent

router.

•Conversely, not detecting the failure of an adjacent

router can result in greater packet loss.

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Step 8 hello-password {hmac-md5 | text} {clear |

encrypted}

password

[level {1 | 2}] [send-only]

Example:

RP/0/RP0/CPU1:router(config-isis-if)#

hello-password text clear mypassword

Specifies that this system include authentication in the

hello packets and requires successful authentication of

the hello packet from the neighbor to establish an

adjacency.

Step 9 end

commit

Example:

RP/0/RP0/CPU0:router(config-isis-if)# end

RP/0/RP0/CPU0:router(config-isis-if)# commit

Saves configuration changes.

•When you issue the end command, the system

prompts you to commit changes:

Uncommitted changes found, commit them before

exiting(yes/no/cancel)?

[cancel]:

–

Entering yes saves configuration changes to the

running configuration file, exits the

configuration session, and returns the router to

EXEC mode.

–

Entering no exits the configuration session and

returns the router to EXEC mode without

committing the configuration changes.

–

Entering cancel leaves the router in the current

configuration session without exiting or

committing the configuration changes.

•Use the commit command to save the configuration

changes to the running configuration file and remain

within the configuration session.

Step 10 show isis [instance

instance-id

] adjacency

[

interface-type

interface-instance

] [detail]

[systemid

system-id

]

Example:

RP/0/RP0/CPU0:router# show isis instance isp

adjacency ipv4

(Optional) Displays IS-IS adjacencies.

Step 11 show isis adjacency-log

Example:

RP/0/RP0/CPU1:router# show isis adjacency-log

(Optional) Displays a log of the most recent adjacency

state transitions.

Command or Action Purpose

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Cisco IOS XR Routing Configuration Guide

Setting SPF Interval for a Single-Topology IPv4 and IPv6 Configuration

This task explains how to make adjustments to the SPF calculation to tune router performance. This task

is optional.

Because the SPF calculation computes routes for a particular topology, the tuning attributes are located

in the router address family configuration submode. SPF calculation computes routes for Level 1 and

Level 2 separately.

When IPv4 and IPv6 address families are used in a single-topology mode, only a single SPF for the IPv4

topology exists. The IPv6 topology “borrows” the IPv4 topology; therefore, no SPF calculation is

required for IPv6. To tune the SPF calculation parameters for single-topology mode, configure the

address-family ipv4 unicast command.

The incremental SPF algorithm can be enabled separately. When enabled, the incremental shortest path

first (ISPF) is not employed immediately. Instead, the full SPF algorithm is used to “seed” the state

information required for the ISPF to run. The startup delay prevents the ISPF from running for a

specified interval after an IS-IS restart (to permit the database to stabilize). After the startup delay

elapses, the ISPF is principally responsible for performing all of the SPF calculations. The reseed

interval enables a periodic running of the full SPF to ensure that the iSFP state remains synchronized.

SUMMARY STEPS

1. configure

2. router isis instance-id

3. address-family {ipv4 | ipv6} [unicast]

4. spf-interval {[initial-wait initial | secondary-wait secondary | maximum-wait maximum]

...}[level {1 | 2}]

5. ispf [startup-delay seconds] [level {1 | 2}]

6. ispf startup-delay seconds [level {1 | 2}]

7. end

commit

8. show isis [instance instance-id] spf-log [level {1 | 2}] [ipv4 | ipv6] [unicast] [ispf | fspf | prc]

[detail] [internal] [last number | first number]

Step 12 show isis [instance

instance-id

] interface [

type

instance

] [brief | detail] [level {1 | 2}]

Example:

RP/0/RP0/CPU0:router# show isis interface POS

0/1/0/1 brief

(Optional) Displays information about the IS-IS

interface.

Step 13 show isis [instance

instance-id

] neighbors

[

interface-type

interface-instance

] [summary]

[detail] [systemid

system-id

]

Example:

RP/0/RP0/CPU0:router# show isis neighbors summary

(Optional) Displays information about IS-IS neighbors.

Command or Action Purpose

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DETAILED STEPS

Command or Action Purpose

Step 1 configure

Example:

RP/0/RP0/CPU0:router# configure

Enters global configuration mode.

Step 2 router isis

instance-id

Example:

RP/0/RP0/CPU0:router(config)# router isis isp

Enables IS-IS routing for the specified routing instance, and

places the router in router configuration mode.

•You can change the level of routing to be performed by

a particular routing instance using the is-type router

configuration command.

Step 3 address-family {ipv4 | ipv6} [unicast]

Example:

RP/0/RP0/CPU0:router(config-isis)#

address-family ipv6 unicast

Specifies the IPv4 or IPv6 address family, and enters router

address family configuration mode.

•This example specifies the unicast IPv6 address family.

Step 4 spf-interval {[initial-wait

initial

secondary-wait

secondary

| maximum-wait

maximum

] ...} [level {1 | 2}]

Example:

RP/0/RP0/CPU0:router(config-isis-af)#

spf-interval initial-wait 10 maximum-wait 30

(Optional) Controls the minimum time between successive

SPF calculations.

•This value imposes a delay in the SPF computation

after an event trigger and enforces a minimum elapsed

time between SPF runs.

•If this value is configured too low, the router can lose

too many CPU resources when the network is unstable.

•Configuring the value too high delays changes in the

network topology that result in lost packets.

•The SPF interval does not apply to the running of the

ISPF because that algorithm runs immediately on

receiving a changed LSP.

Step 5 ispf [startup-delay

seconds

] [level {1 | 2}]

Example:

RP/0/RP0/CPU0:router(config-isis-af)# ispf

(Optional) Configures incremental IS-IS ISPF to calculate

network topology.

Step 6 ispf startup-delay

seconds

[level {1 | 2}]

Example:

RP/0/RP0/CPU0:router(config-isis-af)# ispf

startup-delay 600

(Optional) Configures the time delay between the starting

of the IS-IS instance and the activation of ISPF.

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Enabling Multicast-Intact for IS-IS

This optional task describes how to enable multicast-intact for IS-IS routes that use IPv4 addresses.

Summary Steps

1. configure

2. router isis instance-id

3. address-family {ipv4 | ipv6} [unicast]

4. mpls traffic-eng multicast-intact

5. end

commit

Step 7 end

commit

Example:

RP/0/RP0/CPU0:router(config-isis-af)# end

RP/0/RP0/CPU0:router(config-isis-af)# commit

Saves configuration changes.

•When you issue the end command, the system prompts

you to commit changes:

Uncommitted changes found, commit them before

exiting(yes/no/cancel)?

[cancel]:

–

Entering yes saves configuration changes to the

running configuration file, exits the configuration

session, and returns the router to EXEC mode.

–

Entering no exits the configuration session and

returns the router to EXEC mode without

committing the configuration changes.

–

Entering cancel leaves the router in the current

configuration session without exiting or

committing the configuration changes.

•Use the commit command to save the configuration

changes to the running configuration file and remain

within the configuration session.

Step 8 show isis [instance

instance-id

] spf-log [level

{1 | 2}] [ipv4 | ipv6] [unicast] [ispf | fspf | prc]

[detail] [internal] [last

number

| first

number

]

Example:

RP/0/RP0/CPU0:router# show isis instance 1

spf-log ipv4

(Optional) Displays how often and why the router has run a

full SPF calculation.

Command or Action Purpose

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DETAILED STEPS

Customizing Routes for IS-IS

This task describes how to perform route functions that include injecting default routes into your IS-IS

routing domain and redistributing routes learned at one IS-IS level into a different level. This task is

optional.

Command or Action Purpose

Step 1 configure

Example:

RP/0/RP0/CPU0:router# configure

Enters global configuration mode.

Step 2 router isis

instance-id

Example:

RP/0/RP0/CPU0:router(config)# router isis isp

Enables IS-IS routing for the specified routing process, and

places the router in router configuration mode. In this

example, the IS-IS instance is called isp.

Step 3 address-family {ipv4 | ipv6} [unicast]

Example:

RP/0/RP0/CPU0:router(config-isis)#

address-family ipv4

Specifies the IPv4 or IPv6 address family, and enters router

address family configuration mode. This example specifies

the unicast IPv4 address family.

Step 4 mpls traffic-eng multicast-intact

Example:

RP/0/RP0/CPU0:router(config-isis)# mpls

traffic-eng multicast-intact

Enables multicast-intact.

Step 5 end

commit

Example:

RP/0/RP0/CPU0:router(config-isis-af)# end

RP/0/RP0/CPU0:router(config-isis-af)# commit

Saves configuration changes.

•When you issue the end command, the system prompts

you to commit changes:

Uncommitted changes found, commit them before

exiting(yes/no/cancel)?

[cancel]:

–

Entering yes saves configuration changes to the

running configuration file, exits the configuration

session, and returns the router to EXEC mode.

–

Entering no exits the configuration session and

returns the router to EXEC mode without

committing the configuration changes.

–

Entering cancel leaves the router in the current

configuration session without exiting or

committing the configuration changes.

•Use the commit command to save the configuration

changes to the running configuration file and remain

within the configuration session.

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SUMMARY STEPS

1. configure

2. router isis instance-id

3. set-overload-bit [on-startup {delay | wait-for-bgp}] [level {1 | 2}]

4. address-family {ipv4 | ipv6} [unicast]

5. default-information originate [route-map map-name]

6. redistribute isis instance [level-1 | level-2 | level-1-2] [metric metric] [metric-type {internal |

external}] policy policy-name]

7. summary-prefix [address/prefix-length] [level {1 | 2}]

summary-prefix [ipv6-prefix/prefix-length] [level {1 | 2}]

8. maximum-paths route-number

9. distance weight [address/prefix-length [route-list-name]]

10. set-attached-bit

11. end

commit

DETAILED STEPS

Command or Action Purpose

Step 1 configure

Example:

RP/0/RP0/CPU0:router# configure

Enters global configuration mode.

Step 2 router isis

instance-id

Example:

RP/0/RP0/CPU0:router(config)# router isis isp

Enables IS-IS routing for the specified routing process, and

places the router in router configuration mode.

•By default, all IS-IS instances are automatically

Level 1 and Level 2. You can change the level of

routing to be performed by a particular routing instance

using the is-type command.

Step 3 set-overload-bit [on-startup {

delay

wait-for-bgp}] [level {1 | 2}]

Example:

RP/0/RP0/CPU0:router(config-isis)#

set-overload-bit

(Optional) Sets the overload bit.

Note The configured overload bit behavior does not apply

to NSF restarts because the NSF restart does not set

the overload bit during restart.

Step 4 address-family {ipv4 | ipv6} [unicast]

Example:

RP/0/RP0/CPU0:router(config-isis)#

address-family ipv6 unicast

Specifies the IPv4 or IPv6 address family, and enters router

address family configuration mode.

•This example specifies the unicast IPv6 address family.

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Step 5 default-information originate [route-map

map-name

]

Example:

RP/0/RP0/CPU0:router(config-isis-af)#

default-information originate

(Optional) Injects a default IPv4 or IPv6 route into an IS-IS

routing domain.

•The route-map keyword and map-name argument

specify the conditions under which the IPv4 or IPv6

default route is advertised.

•If the route-map keyword is omitted, then the IPv4 or

IPv6 default route is unconditionally advertised at

Level 2.

Step 6 redistribute isis

instance

[level-1 | level-2 |

level-1-2] [metric

metric

] [metric-type

{internal | external}] [policy

policy-name

]

Example:

RP/0/RP0/CPU0:router(config-isis-af)#

redistribute isis 2 level-1

(Optional) Redistributes routes from one IS-IS instance into

another instance.

•In this example, an IS-IS instance redistributes IS-IS

instance 2 routes into its Level 1 area.

Step 7 summary-prefix [

address

prefix-length

] [level

{1 | 2}]

summary-prefix [

ipv6-prefix

prefix-length

]

[level {1 | 2}]

Example:

RP/0/RP0/CPU0:router(config-isis-af)#

summary-prefix 10.1.0.0/16 level 1

RP/0/RP0/CPU0:router(config-isis-af)#

summary-prefix 3003:xxxx::/24 level 1

(Optional) Allows a Level 1-2 router to summarize Level 1

IPv4 and IPv6 prefixes at Level 2, instead of advertising the

Level 1 prefixes directly when the router advertises the

summary.

•This example specifies an IPv4 address and mask.

•This example specifies an IPv6 prefix, and the

command must be in the form documented in RFC 2373

in which the address is specified in hexadecimal using

16-bit values between colons.

•Note that IPv6 prefixes must be configured only in the

IPv6 router address family configuration submode, and

IPv4 prefixes in the IPv4 router address family

configuration submode.

Step 8 maximum-paths

route-number

Example:

RP/0/RP0/CPU0:router(config-isis-af)#

maximum-paths 16

(Optional) Configures the maximum number of parallel

paths allowed in a routing table.

Step 9 distance

weight

[

address

prefix-length

[

route-list-name

]]

Example:

RP/0/RP0/CPU0:router(config-isis-af)# distance

(Optional) Defines the administrative distance assigned to

routes discovered by the IS-IS protocol.

•A different administrative distance may be applied for

IPv4 and IPv6.

Command or Action Purpose

Implementing IS-IS on Cisco IOS XR Software

Configuration Examples for Implementing IS-IS on Cisco IOS XR Software

RC-122

Cisco IOS XR Routing Configuration Guide

Configuration Examples for Implementing IS-IS on Cisco IOS XR

Software

This section provides the following configuration examples:

•Configuring Single-Topology IS-IS for IPv6: Example, page RC-122

•Configuring Multitopology IS-IS for IPv6: Example, page RC-123

•Redistributing IS-IS Routes Between Multiple Instances: Example, page RC-123

Configuring Single-Topology IS-IS for IPv6: Example

The following example shows single-topology mode being enabled, an IS-IS instance being created, the

NET being defined, IPv6 being configured along with IPv4 on an interface, and IPv4 link topology being

used for IPv6.

This configuration allows POS interface 0/3/0/0 to form adjacencies for both IPv4 and IPv6 addresses.

router isis isp

net 49.0000.0000.0001.00

address-family ipv6 unicast

single-topology

interface POS0/3/0/0

Step 10 set-attached-bit

Example:

RP/0/RP0/CPU0:router(config-isis-af)#

set-attached-bit

(Optional) Configures an IS-IS instance with an attached bit

in the Level 1 LSP.

Step 11 end

commit

Example:

RP/0/RP0/CPU0:router(config-isis-af)# end

RP/0/RP0/CPU0:router(config-isis-af)# commit

Saves configuration changes.

•When you issue the end command, the system prompts

you to commit changes:

Uncommitted changes found, commit them before

exiting(yes/no/cancel)?

[cancel]:

–

Entering yes saves configuration changes to the

running configuration file, exits the configuration

session, and returns the router to EXEC mode.

–

Entering no exits the configuration session and

returns the router to EXEC mode without

committing the configuration changes.

–

Entering cancel leaves the router in the current

configuration session without exiting or

committing the configuration changes.

•Use the commit command to save the configuration

changes to the running configuration file and remain

within the configuration session.

Command or Action Purpose

Implementing IS-IS on Cisco IOS XR Software

Configuration Examples for Implementing IS-IS on Cisco IOS XR Software

RC-123

Cisco IOS XR Routing Configuration Guide

address-family ipv4 unicast

address-family ipv6 unicast

exit

interface POS0/3/0/0

ipv4 address 10.0.1.3 255.255.255.0

ipv6 address 2001::1/64

Configuring Multitopology IS-IS for IPv6: Example

The following example shows multitopology IS-IS being configured in IPv6. You need not enable IS-IS

for IPv6 globally on the router.

router isis isp

net 49.0000.0000.0001.00

interface POS0/3/0/0

address-family ipv6 unicast

metric-style wide level 1

exit

interface POS0/3/0/0

ipv6 address 2001::1/64

Redistributing IS-IS Routes Between Multiple Instances: Example

The following example shows the attached bit being set for a Level 1 instance. This example shows the

other Level 1 routers in the area being informed that this router is a suitable candidate to get from the

area to the backbone. The Level 1 instance is also propagating routes to the Level 2 instance using

redistribution. Note that the administrative distance is explicitly configured higher on the Level 2

instance to ensure that Level 1 routes are preferred.

router isis 1

is-type level-2-only

net 49.0001.0001.0001.0001.00

address-family ipv4 unicast

distance 116

redistribute isis 2 level 2

interface POS0/3/0/0

address-family ipv4 unicast

router isis 2

is-type level-1

net 49.0002.0001.0001.0002.00

address-family ipv4 unicast

set-attached-bit

interface POS0/1/0/0

address-family ipv4 unicast

Implementing IS-IS on Cisco IOS XR Software

Where to Go Next

RC-124

Cisco IOS XR Routing Configuration Guide

Where to Go Next

To implement more IP routing protocols, see the following document modules:

•Implementing OSPF on Cisco IOS XR Software

•Implementing BGP on Cisco IOS XR Software

Additional References

The following sections provide references related to implementing IS-IS on Cisco IOS XR software.

Related Documents

Standards

MIBs

Related Topic Document Title

IS-IS commands: complete command syntax,

command modes, command history, defaults, usage

guidelines, and examples

Cisco IOS XR Routing Command Reference, Release 3.2

MPLS TE feature information Implementing MPLS Traffic Engineering on Cisco IOS XR Software

module in the Cisco IOS XR Multiprotocol Label Switching

Configuration Guide, Release 3.2

Standards Title

Draft-ietf-isis-ipv6-05.txt Routing IPv6 with IS-IS, by Christian E. Hopps

Draft-ietf-isis-wg-multi-topology-06.txt M-ISIS: Multi Topology (MT) Routing in IS-IS, by Tony Przygienda,

Naiming Shen, and Nischal Sheth

Draft-ietf-isis-traffic-05.txt IS-IS Extensions for Traffic Engineering, by Henk Smit and Toni Li

Draft-ietf-isis-restart-04.txt Restart Signalling for IS-IS, by M. Shand and Les Ginsberg

Draft-ietf-isis-igp-p2p-over-lan-05.txt Point-to-point operation over LAN in link-state routing protocols, by

Naiming Shen

MIBs MIBs Link

There are no applicable MIBs for this module. To locate and download MIBs for selected platforms using

Cisco IOS XR software, use the Cisco MIB Locator found at the

following URL:

http://cisco.com/public/sw-center/netmgmt/cmtk/mibs.shtml

Implementing IS-IS on Cisco IOS XR Software

Additional References

RC-125

Cisco IOS XR Routing Configuration Guide

RFCs

Technical Assistance

RFCs Title

RFC 1142 OSI IS-IS Intra-domain Routing Protocol

RFC 1195 Use of OSI IS-IS for Routing in TCP/IP and Dual Environments

RFC 2763 Dynamic Hostname Exchange Mechanism for IS-IS

RFC 2966 Domain-wide Prefix Distribution with Two-Level IS-IS

RFC 2973 IS-IS Mesh Groups

RFC 3277 IS-IS Transient Blackhole Avoidance

RFC 3373 Three-Way Handshake for IS-IS Point-to-Point Adjacencies

RFC 3567 IS-IS Cryptographic Authentication

Description Link

The Cisco Technical Support website contains

thousands of pages of searchable technical content,

including links to products, technologies, solutions,

technical tips, and tools. Registered Cisco.com users

can log in from this page to access even more content.

http://www.cisco.com/techsupport

Implementing IS-IS on Cisco IOS XR Software

Additional References

RC-126

Cisco IOS XR Routing Configuration Guide

RC-127

Cisco IOS XR Routing Configuration Guide

Implementing OSPF on Cisco IOS XR Software

Open Shortest Path First (OSPF) is an Interior Gateway Protocol (IGP) developed by the OSPF working

group of the Internet Engineering Task Force (IETF). Designed expressly for IP networks, OSPF

supports IP subnetting and tagging of externally derived routing information. OSPF also allows packet

authentication and uses IP multicast when sending and receiving packets.

Implementing OSPF version 3 (OSPFv3) expands on OSPF Version 2, to provide support for IPv6

routing prefixes.

This module describes the concepts and tasks you need to implement both versions of OSPF on your

Cisco IOS XR router. The term “OSPF” implies both versions of the routing protocol, unless otherwise

noted.

Note For more information about OSPF on the Cisco IOS XR software and complete descriptions of the OSPF

commands listed in this module, see the “Related Documents” section of this module. To locate

documentation for other commands that might appear during execution of a configuration task, search

online in the Cisco IOS XR software master command index.

Feature History for Implementing OSPF on Cisco IOS XR Software

Contents

•Prerequisites for Implementing OSPF on Cisco IOS XR Software, page RC-128

•Information About Implementing OSPF on Cisco IOS XR Software, page RC-128

•How to Implement OSPF on Cisco IOS XR Software, page RC-144

•Configuration Examples for Implementing OSPF on Cisco IOS XR Software, page RC-187

•Where to Go Next, page RC-192

•Additional References, page RC-193

Release Modification

Release 2.0 This feature was introduced on the Cisco CRS-1.

Release 3.0 No modification.

Release 3.2 Support was added for the Cisco XR 12000 Series Router.

Release 3.2.2 Support was added for the multicast-intact feature.

Implementing OSPF on Cisco IOS XR Software

Prerequisites for Implementing OSPF on Cisco IOS XR Software

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Cisco IOS XR Routing Configuration Guide

Prerequisites for Implementing OSPF on Cisco IOS XR Software

The following are prerequisites for implementing OSPF on Cisco IOS XR Software:

•You must be in a user group associated with a task group that includes the proper task IDs for OSPF

commands. Task IDs for commands are listed in the Cisco IOS XR Task ID Reference Guide. For

detailed information about user groups and task IDs, see the Configuring AAA Services on Cisco IOS

XR Software module of the Cisco IOS XR System Security Configuration Guide.

•Configuration tasks for OSPFv3 assume that you are familiar with IPv6 addressing and basic

configuration. See the Implementing Network Stack IPv4 and IPv6 on Cisco IOS XR Software

module of the Cisco IOS XR IP Addresses and Services Configuration Guide for information on

IPv6 routing and addressing.

•Before you enable OSPFv3 on an interface, you must perform the following tasks:

–

Complete the OSPF network strategy and planning for your IPv6 network. For example, you

must decide whether multiple areas are required.

–

Enable IPv6 on the interface.

•Configuring authentication (IP Security) is an optional task. If you choose to configure

authentication, you must first decide whether to configure plain text or Message Digest 5 (MD5)

authentication, and whether the authentication applies to an entire area or specific interfaces.

Information About Implementing OSPF on Cisco IOS XR

Software

To implement OSPF you need to understand the following concepts:

•OSPF Functional Overview, page RC-129

•Key Features Supported in the Cisco IOS XR OSPF Implementation, page RC-130

•Comparison of Cisco IOS XR OSPFv3 and OSPFv2, page RC-131

•Importing Addresses into OSPFv3, page RC-131

•OSPF Hierarchical CLI and CLI Inheritance, page RC-131

•OSPF Routing Components, page RC-132

•OSPF Process and Router ID, page RC-134

•Supported OSPF Network Types, page RC-135

•Route Authentication Methods for OSPF Version 2, page RC-135

•Neighbors and Adjacency for OSPF, page RC-136

•Designated Router (DR) for OSPF, page RC-136

•Default Route for OSPF, page RC-137

•Link-State Advertisement Types for OSPF Version 2, page RC-137

•Link-State Advertisement Types for OSPFv3, page RC-137

•Virtual Link and Transit Area for OSPF, page RC-138

•Route Redistribution for OSPF, page RC-139

•OSPF Shortest Path First Throttling, page RC-139

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•Nonstop Forwarding for OSPF Version 2, page RC-140

•Load Balancing in OSPF Version 2 and OSPFv3, page RC-141

OSPF Functional Overview

OSPF is a routing protocol for IP. It is a link-state protocol, as opposed to a distance-vector protocol. A

link-state protocol makes its routing decisions based on the states of the links that connect source and

destination machines. The state of the link is a description of that interface and its relationship to its

neighboring networking devices. The interface information includes the IP address of the interface,

network mask, type of network to which it is connected, routers connected to that network, and so on.

This information is propagated in various types of link-state advertisements (LSAs).

A router stores the collection of received link-state advertisement (LSA) data in a link-state database.

This database includes LSA data for the links of the router. The contents of the database, when subjected

to the Dijkstra algorithm, extract data to create an OSPF routing table. The difference between the

database and the routing table is that the database contains a complete collection of raw data; the routing

table contains a list of shortest paths to known destinations through specific router interface ports.

OSPF is the IGP of choice because it scales to large networks. It uses areas to partition the network into

more manageable sizes and to introduce hierarchy in the network. A router is attached to one or more

areas in a network. All of the networking devices in an area maintain the same complete database

information about the link states in their area only. They do not know about all link states in the network.

The agreement of the database information among the routers in the area is called convergence.

At the intradomain level, OSPF can import routes learned using Intermediate System-to-Intermediate

System (IS-IS). OSPF routes can also be exported into IS-IS. At the interdomain level, OSPF can import

routes learned using Border Gateway Protocol (BGP). OSPF routes can be exported into BGP.

Unlike Routing Information Protocol (RIP), OSPF does not provide periodic routing updates. On

becoming neighbors, OSPF routers establish an adjacency by exchanging and synchronizing their

databases. After that, only changed routing information is propagated. Every router in an area advertises

the costs and states of its links, sending this information in an LSA. This state information is sent to all

OSPF neighbors one hop away. All the OSPF neighbors, in turn, send the state information unchanged.

This flooding process continues until all devices in the area have the same link-state database.

To determine the best route to a destination, the software sums all of the costs of the links in a route to

a destination. After each router has received routing information from the other networking devices, it

runs the shortest path first (SPF) algorithm to calculate the best path to each destination network in the

database.

The networking devices running OSPF detect topological changes in the network, flood link-state

updates to neighbors, and quickly converge on a new view of the topology. Each OSPF router in the

network soon has the same topological view again. OSPF allows multiple equal-cost paths to the same

destination. Since all link-state information is flooded and used in the SPF calculation, multiple equal

cost paths can be computed and used for routing.

On broadcast and nonbroadcast multiaccess (NBMA) networks, the designated router (DR) or backup

DR performs the LSA flooding. On point-to-point networks, flooding simply exits an interface directly

to a neighbor.

OSPF runs directly on top of IP; it does not use TCP or User Datagram Protocol (UDP). OSPF performs

its own error correction by means of checksums in its packet header and LSAs.

In OSPFv3, the fundamental concepts are the same as OSPF Version 2, except that support is added for

the increased address size of IPv6. New LSA types are created to carry IPv6 addresses and prefixes, and

the protocol runs on an individual link basis rather than on an individual IP-subnet basis.

Implementing OSPF on Cisco IOS XR Software

Information About Implementing OSPF on Cisco IOS XR Software

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Cisco IOS XR Routing Configuration Guide

OSPF typically requires coordination among many internal routers: Area Border Routers (ABRs), which

are routers attached to multiple areas, and Autonomous System Border Routers (ASBRs) that export

reroutes from other sources (for example, IS-IS, BGP, or static routes) into the OSPF topology. At a

minimum, OSPF-based routers or access servers can be configured with all default parameter values, no

authentication, and interfaces assigned to areas. If you intend to customize your environment, you must

ensure coordinated configurations of all routers.

Key Features Supported in the Cisco IOS XR OSPF Implementation

The Cisco IOS XR implementation of OSPF conforms to the OSPF Version 2 and OSPF Version 3

specifications detailed in the Internet RFC 2328 and RFC 2740, respectively.

The following key features are supported in the Cisco IOS XR implementation:

•Hierarchy—CLI hierarchy is supported.

•Inheritance—CLI inheritance is supported.

•Stub areas—Definition of stub areas is supported.

•NSF—Nonstop forwarding is supported.

•SPF throttling—Shortest path first throttling feature is supported.

•LSA throttling—LSA throttling feature is supported.

•Fast convergence—SPF and LSA throttle timers are set, configuring fast convergence. The OSPF

LSA throttling feature provides a dynamic mechanism to slow down LSA updates in OSPF during

network instability. LSA throttling also allows faster OSPF convergence by providing LSA rate

limiting in milliseconds.

•Route redistribution—Routes learned using any IP routing protocol can be redistributed into any

other IP routing protocol.

•Authentication—Plain text and MD5 authentication among neighboring routers within an area is

supported.

•Routing interface parameters—Configurable parameters supported include interface output cost,

retransmission interval, interface transmit delay, router priority, router “dead” and hello intervals,

and authentication key.

•Virtual links—Virtual links are supported.

•Not-so-stubby area (NSSA)—RFC 1587 is supported.

•OSPF over demand circuit—RFC 1793 is supported.

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Comparison of Cisco IOS XR OSPFv3 and OSPFv2

Much of the OSPFv3 protocol is the same as in OSPFv2. OSPFv3 is described in RFC 2740.

The key differences between the Cisco IOS XR OSPFv3 and OSPFv2 protocols are as follows:

•OSPFv3 expands on OSPFv2 to provide support for IPv6 routing prefixes and the larger size of IPv6

addresses.

•When using an NBMA interface in OSPFv3, users must manually configure the router with the list

of neighbors. Neighboring routers are identified by the link local address of the attached interface

of the neighbor.

•Unlike in OSPFv2, multiple OSPFv3 processes can be run on a link.

•LSAs in OSPFv3 are expressed as “prefix and prefix length” instead of “address and mask.”

•The router ID is a 32-bit number with no relationship to an IPv6 address.

Importing Addresses into OSPFv3

When importing into OSPFv3 the set of addresses configured on an OSPFv3 interface, users cannot

select specific addresses to be imported. Either all addresses are imported or no addresses are imported.

OSPF Hierarchical CLI and CLI Inheritance

Cisco IOS XR software introduces new OSPF configuration fundamentals consisting of hierarchical

CLI and CLI inheritance.

Hierarchical CLI is the grouping of related network component information at defined hierarchical

levels such as at the router, area, and interface levels. Hierarchical CLI allows for easier configuration,

maintenance, and troubleshooting of OSPF configurations. When configuration commands are

displayed together in their hierarchical context, visual inspections are simplified. Hierarchical CLI is

intrinsic for CLI inheritance to be supported.

With CLI inheritance support, you need not explicitly configure a parameter for an area or interface. In

Cisco IOS XR, the parameters of interfaces in the same area can be exclusively configured with a single

command, or parameter values can be inherited from a higher hierarchical level—such as from the area

configuration level or the router ospf configuration levels.

For example, the hello interval value for an interface is determined by this precedence “IF” statement:

If the hello interval command is configured at the interface configuration level, then use the

interface configured value, else

If the hello interval command is configured at the area configuration level, then use the area

configured value, else

If the hello interval command is configured at the router ospf configuration level, then use the

router ospf configured value, else

Use the default value of the command.

Implementing OSPF on Cisco IOS XR Software

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Cisco IOS XR Routing Configuration Guide

Tip Understanding hierarchical CLI and CLI inheritance saves you considerable configuration time. See the

“Configuring Authentication at Different Hierarchical Levels for OSPF Version 2” section on

page RC-155 to understand how to implement these fundamentals. In addition, Cisco IOS XR examples

are provided in the “Configuration Examples for Implementing OSPF on Cisco IOS XR Software”

section on page RC-187.

OSPF Routing Components

Before implementing OSPF, you must know what the routing components are and what purpose they

serve. They consist of the autonomous system, area types, interior routers, ABRs, and ASBRs.

Figure 6 illustrates the routing components in an OSPF network topology.

Figure 6 OSPF Routing Components

Autonomous Systems

The autonomous system is a collection of networks, under the same administrative control, that share

routing information with each other. An autonomous system is also referred to as a routing domain.

Figure 6 shows two autonomous systems: A and B. An autonomous system can consist of one or more

OSPF areas.

88721

Area 2

stub area

Area 0

backbone

Area 1

Area 3

ABR 2

OSPF Domain

(BGP autonomous

system 109)

OSPF Domain

(BGP autonomous

system 65200)

ABR 1

ASBR 1

ASBR 2

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Cisco IOS XR Routing Configuration Guide

Areas

Areas allow the subdivision of an autonomous system into smaller, more manageable networks or sets

of adjacent networks. As shown in Figure 6, autonomous system A consists of three areas: Area 0, Area

1, and Area 2.

OSPF hides the topology of an area from the rest of the autonomous system. The network topology for

an area is visible only to routers inside that area. When OSPF routing is within an area, it is called

intra-area routing. This routing limits the amount of link-state information flood into the network,

reducing routing traffic. It also reduces the size of the topology information in each router, conserving

processing and memory requirements in each router.

Also, the routers within an area cannot see the detailed network topology outside the area. Because of

this restricted view of topological information, you can control traffic flow between areas and reduce

routing traffic when the entire autonomous system is a single routing domain.

Backbone Area

A backbone area is responsible for distributing routing information between multiple areas of an

autonomous system. OSPF routing occurring outside of an area is called interarea routing.

The backbone itself has all properties of an area. It consists of ABRs, routers, and networks only on the

backbone. As shown in Figure 6, Area 0 is an OSPF backbone area. Any OSPF backbone area has a

reserved area ID of 0.0.0.0.

Stub Area

A stub area is an area that does not accept or detailed network information external to the area. A stub

area typically has only one router that interfaces the area to the rest of the autonomous system. The stub

ABR advertises a single default route to external destinations into the stub area. Routers within a stub

area use this route for destinations outside the area and the autonomous system. This relationship

conserves LSA database space that would otherwise be used to store external LSAs flooded into the area.

In Figure 6, Area 2 is a stub area that is reached only through ABR 2. Area 0 cannot be a stub area.

Not-so-Stubby Area (NSSA)

NSSA is similar to the stub area. NSSA does not flood Type 5 external LSAs from the core into the area,

but can import autonomous system external routes in a limited fashion within the area.

NSSA allows importing of Type 7 autonomous system external routes within an NSSA area by

redistribution. These Type 7 LSAs are translated into Type 5 LSAs by NSSA ABRs, which are flooded

throughout the whole routing domain. Summarization and filtering are supported during the translation.

Use NSSA to simplify administration if you are a network administrator that must connect a central site

using OSPF to a remote site that is using a different routing protocol.

Before NSSA, the connection between the corporate site border router and remote router could not be

run as an OSPF stub area because routes for the remote site could not be redistributed into a stub area,

and two routing protocols needed to be maintained. A simple protocol like RIP was usually run and

handled the redistribution. With NSSA, you can extend OSPF to cover the remote connection by

defining the area between the corporate router and remote router as an NSSA. Area 0 cannot be an

NSSA.

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Routers

The OSPF network is composed of ABRs, ASBRs, and interior routers.

Area Border Routers (ABR)

ABRs are routers with multiple interfaces that connect directly to networks in two or more areas. An

ABR runs a separate copy of the OSPF algorithm and maintains separate routing data for each area that

is attached to, including the backbone area. ABRs also send configuration summaries for their attached

areas to the backbone area, which then distributes this information to other OSPF areas in the

autonomous system. In Figure 6, there are two ABRs. ABR 1 interfaces Area 1 to the backbone area.

ABR 2 interfaces the backbone Area 0 to Area 2, a stub area.

Autonomous System Boundary Routers (ASBR)

ASBRs provide connectivity from one autonomous system to another system. ASBRs exchange their

autonomous system routing information with boundary routers in other autonomous systems. Every

router inside an autonomous system knows how to reach the boundary routers for its autonomous

system.

ASBRs can import external routing information from other protocols like BGP and redistribute them as

AS-external (ASE) Type 5 LSAs to the OSPF network. If the Cisco IOS XR router is an ASBR, you can

configure it to advertise VIP addresses for content as autonomous system external routes. In this way,

ASBRs flood information about external networks to routers within the OSPF network.

ASBR routes can be advertised as a Type 1 or Type 2 ASE. The difference between Type 1 and Type 2

is how the cost is calculated. For a Type 2 ASE, only the external cost (metric) is considered when

multiple paths to the same destination are compared. For a Type 1 ASE, the combination of the external

cost and cost to reach the ASBR is used. Type 2 external cost is the default and is always more costly

than an OSPF route and used only if no OSPF route exists.

Interior Routers

The interior routers (such as R1 in Figure 6) attached to one area (for example, all the interfaces reside

in the same area).

OSPF Process and Router ID

An OSPF process is a logical routing entity running OSPF in a physical router. This logical routing entity

should not be confused with the logical routing feature that allows a system administrator (known as the

Cisco IOS XR Owner) to partition the physical box into separate routers.

A physical router can run multiple OSPF processes, although the only reason to do so would be to

connect two or more OSPF domains. Each process has its own link-state database. The routes in the

routing table are calculated from the link-state database. One OSPF process does not share routes with

another OSPF process unless the routes are redistributed.

Each OSPF process is identified by a router ID. The router ID must be unique across the entire routing

domain. OSPFv2 obtains a router ID from the following sources, in order of decreasing preference:

OSPF attempts to obtain a router ID in the following ways (in order of preference):

•The 32-bit numeric value specified by the OSPF router-id command in router configuration mode.

(This value can be any 32-bit value. It is not restricted to the IPv4 addresses assigned to interfaces

on this router, and need not be a routable IPv4 address.)

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•The primary IPv4 address of the interface specified by the OSPF router-id command.

•The 32-bit numeric value specified by the router-id command in global configuration mode. (This

value must be an IPv4 address assigned to an interface on this router.)

•By using the highest IPv4 address on a loopback interface in the system if the router is booted with

saved loopback address configuration.

•The primary IPv4 address of an interface over which this OSPF process is running.

We recommend that the router ID be set by the router-id command in router configuration mode.

Separate OSPF processes could share the same router ID, in which case they cannot reside in the same

OSPF routing domain.

Supported OSPF Network Types

OSPF classifies different media into the following three types of networks by default:

•NBMA networks (POS)

•Point-to-point networks (POS)

•Broadcast networks (Gigabit Ethernet)

You can configure your Cisco IOS XR network as either a broadcast or an NBMA network. Using this

feature, you can configure broadcast networks as NBMA networks when, for example, you have routers

in your network that do not support multicast addressing.

Route Authentication Methods for OSPF Version 2

OSPF Version 2 supports two types of route authentication: plain text authentication and MD5

authentication. By default, no authentication is enabled (referred to as null authentication in RFC 2178).

Both plain text and MD5 authentication are performed on changed routing information that arrive on an

interface. The sender and receiver must know the authentication password or key. For both types of

authentication, a router sends a routing update packet with a key and corresponding key number. The

receiving router checks the key number and key against its own stored key number and key. If the key

numbers and keys match, the router accepts the routing update packet. If they do not match, the routing

update is discarded.

Plain Text Authentication

Plain text authentication (also known as Type 1 authentication) uses a password that travels on the

physical medium and is easily visible to someone that does not have access permission and could use

the password to infiltrate a network. Therefore, plain text authentication does not provide security. It

might protect against a faulty implementation of OSPF or a misconfigured OSPF interface trying to send

erroneous OSPF packets.

MD5 Authentication

MD5 authentication provides a means of security. No password travels on the physical medium. Instead,

the router uses MD5 to produce a message digest of the OSPF packet plus the key, which is sent on the

physical medium. Using MD5 authentication prevents a router from accepting unauthorized or

deliberately malicious routing updates, which could compromise your network security by diverting

your traffic.

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Note MD5 authentication supports multiple keys, requiring that a key number be associated with a key.

Authentication Strategies

Authentication can be specified for an entire process or area, or on an interface or a virtual link. An

interface or virtual link can be configured for only one type of authentication, not both. Authentication

configured for an interface or virtual link overrides authentication configured for the area or process.

If you intend for all interfaces in an area to use the same type of authentication, you can configure fewer

commands if you use the area authentication command (and specify the message-digest keyword if

you want the entire area to use MD5 authentication). This strategy requires fewer commands than

specifying authentication for each interface.

Key Rollover

To support the changing of a plain text key or MD5 key in an operational network without disrupting

OSPF adjacencies (and hence the topology), a key rollover mechanism is supported. As a network

administrator configures the new key into the multiple networking devices that communicate, some time

exists when different devices are using both a new key and an old key. If an interface is configured with

a new key, the software sends two copies of the same packet, each authenticated by the old key and new

key. The software tracks which devices start using the new key, and the software stops sending duplicate

packets after it detects that all of its neighbors are using the new key. The software then discards the old

key. The network administrator must then remove the old key from each the configuration file of each

router.

Neighbors and Adjacency for OSPF

Routers that share a segment (Layer 2 link between two interfaces) become neighbors on that segment.

OSPF uses the hello protocol as a neighbor discovery and keep alive mechanism. The hello protocol

involves receiving and periodically sending hello packets out each interface. The hello packets list all

known OSPF neighbors on the interface. Routers become neighbors when they see themselves listed in

the hello packet of the neighbor. After two routers are neighbors, they may proceed to exchange and

synchronize their databases, which creates an adjacency. On broadcast and NBMA networks all

neighboring routers have an adjacency.

Designated Router (DR) for OSPF

On point-to-point and point-to-multipoint networks, the Cisco IOS XR software floods routing updates

to immediate neighbors. No DR or backup DR (BDR) exists; all routing information is flooded to each

router.

On broadcast or NBMA segments only, OSPF minimizes the amount of information being exchanged on

a segment by choosing one router to be a DR and one router to be a BDR. Thus, the routers on the

segment have a central point of contact for information exchange. Instead of each router exchanging

routing updates with every other router on the segment, each router exchanges information with the DR

and BDR. The DR and BDR relay the information to the other routers. On broadcast network segments

the number of OSPF packets is further reduced by the DR and BDR sending such OSPF updates to a

multicast IP address that all OSPF routers on the network segment are listening on.

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The software looks at the priority of the routers on the segment to determine which routers are the DR

and BDR. The router with the highest priority is elected the DR. If there is a tie, then the router with the

higher router ID takes precedence. After the DR is elected, the BDR is elected the same way. A router

with a router priority set to zero is ineligible to become the DR or BDR.

Default Route for OSPF

Type 5 (ASE) LSAs are generated and flooded to all areas except stub areas. For the routers in a stub

area to be able to route packets to destinations outside the stub area, a default route is injected by the

ABR attached to the stub area.

The cost of the default route is 1 (default) or is determined by the value specified in the default-cost

command.

Link-State Advertisement Types for OSPF Version 2

Each of the following LSA types has a different purpose:

•Router LSA (Type 1)—Describes the links that the router has within a single area, and the cost of

each link. These LSAs are flooded within an area only. The LSA indicates if the router can compute

paths based on quality of service (QoS), whether it is an ABR or ASBR, and if it is one end of a

virtual link. Type 1 LSAs are also used to advertise stub networks.

•Network LSA (Type 2)—Describes the link state and cost information for all routers attached a

multiaccess network segment. This LSA lists all the routers that have interfaces attached to the

network segment. It is the job of the designated router of a network segment to generate and track

the contents of this LSA.

•Summary LSA for ABRs (Type 3)—Advertises internal networks to routers in other areas (interarea

routes). Type 3 LSAs may represent a single network or a set of networks aggregated into one prefix.

Only ABRs generate summary LSAs.

•Summary LSA for ASBRs (Type 4)—Advertises and ASBR and the cost to reach it. Routers that

are trying to reach an external network use these advertisements to determine the best path to the

next hop. ABRs generate Type 4 LSAs.

•Autonomous system external LSA (Type 5)—Redistributes routes from another autonomous

system, usually from a different routing protocol into OSPF.

Link-State Advertisement Types for OSPFv3

Each of the following LSA types has a different purpose:

•Router LSA (Type 1)—Describes the link state and costs of a the router link to the area. These LSAs

are flooded within an area only. The LSA indicates whether the router is an ABR or ASBR and if it

is one end of a virtual link. Type 1 LSAs are also used to advertise stub networks. In OSPFv3, these

LSAs have no address information and are network protocol independent. In OSPFv3, router

interface information may be spread across multiple router LSAs. Receivers must concatenate all

router LSAs originated by a given router before running the SPF calculation.

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•Network LSA (Type 2)—Describes the link state and cost information for all routers attached to a

multiaccess network segment. This LSA lists all OSPF routers that have interfaces attached to the

network segment. Only the elected designated router for the network segment can generate and track

the network LSA for the segment. In OSPFv3, network LSAs have no address information and are

network-protocol-independent.

•Interarea-prefix LSA for ABRs (Type 3)—Advertises internal networks to routers in other areas

(interarea routes). Type 3 LSAs may represent a single network or set of networks aggregated into

one prefix. Only ABRs generate Type 3 LSAs. In OSPFv3, addresses for these LSAs are expressed

as “prefix and prefix length” instead of “address and mask.” The default route is expressed as a

prefix with length 0.

•Interarea-router LSA for ASBRs (Type 4)—Advertises an ASBR and the cost to reach it. Routers

that are trying to reach an external network use these advertisements to determine the best path to

the next hop. ABRs generate Type 4 LSAs.

•Autonomous system external LSA (Type 5)—Redistributes routes from another autonomous

system, usually from a different routing protocol into OSPF. In OSPFv3, addresses for these LSAs

are expressed as “prefix and prefix length” instead of “address and mask.” The default route is

expressed as a prefix with length 0.

•Link LSA (Type 8)—Has link-local flooding scope and is never flooded beyond the link with which

it is associated. Link LSAs provide the link-local address of the router to all other routers attached

to the link or network segment, inform other routers attached to the link of a list of IPv6 prefixes to

associate with the link, and allow the router to assert a collection of Options bits to associate with

the network LSA that is originated for the link.

•Intra-area-prefix LSAs (Type 9)—A router can originate multiple intra-area-prefix LSAs for every

router or transit network, each with a unique link-state ID. The link-state ID for each

intra-area-prefix LSA describes its association to either the router LSA or network LSA and

contains prefixes for stub and transit networks.

An address prefix occurs in almost all newly defined LSAs. The prefix is represented by three fields:

Prefix Length, Prefix Options, and Address Prefix. In OSPFv3, addresses for these LSAs are expressed

as “prefix and prefix length” instead of “address and mask.” The default route is expressed as a prefix

with length 0.

Inter-area-prefix and intra-area-prefix LSAs carry all IPv6 prefix information that, in IPv4, is included

in router LSAs and network LSAs. The Options field in certain LSAs (router LSAs, network LSAs,

interarea-router LSAs, and link LSAs) has been expanded to 24 bits to provide support for OSPF in IPv6.

In OSPFv3, the sole function of link-state ID in interarea-prefix LSAs, interarea-router LSAs, and

autonomous system external LSAs is to identify individual pieces of the link-state database. All

addresses or router IDs that are expressed by the link-state ID in OSPF Version 2 are carried in the body

of the LSA in OSPFv3.

Virtual Link and Transit Area for OSPF

In OSPF, routing information from all areas is first summarized to the backbone area by ABRs. The same

ABRs, in turn, propagate such received information to their attached areas. Such hierarchical

distribution of routing information requires that all areas be connected to the backbone area (Area 0).

Occasions might exist for which an area must be defined, but it cannot be physically connected to Area 0.

Examples of such an occasion might be if your company makes a new acquisition that includes an OSPF

area, or if Area 0 itself is partitioned.

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In the case in which an area cannot be connected to Area 0, you must configure a virtual link between

that area and Area 0. The two endpoints of a virtual link are ABRs, and the virtual link must be

configured in both routers. The common nonbackbone area to which the two routers belong is called a

transit area. A virtual link specifies the transit area and the router ID of the other virtual endpoint (the

other ABR).

A virtual link cannot be configured through a stub area or NSSA.

Figure 7 illustrates a virtual link from Area 3 to Area 0.

Figure 7 Virtual Link to Area 0

Route Redistribution for OSPF

Redistribution allows different routing protocols to exchange routing information. This technique can

be used to allow connectivity to span multiple routing protocols. It is important to remember that the

redistribute command controls redistribution into an OSPF process and not from OSPF. See the

“Configuration Examples for Implementing OSPF on Cisco IOS XR Software” section on page RC-187

for an example of route redistribution for OSPF.

OSPF Shortest Path First Throttling

OSPF SPF throttling makes it possible to configure SPF scheduling in millisecond intervals and to

potentially delay SPF calculations during network instability. SPF is scheduled to calculate the Shortest

Path Tree (SPT) when there is a change in topology. One SPF run may include multiple topology change

events.

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Backbone

Area 1

Transit Area

Area 3

ABR 1ABR 2

OSPF Domain (BGP autonomous system 109)

ABR 3

Router ID 5.5.5.5 Router ID 4.4.4.4

ASBR 1

ASBR 2

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The interval at which the SPF calculations occur is chosen dynamically and based on the frequency of

topology changes in the network. The chosen interval is within the boundary of the user-specified value

ranges. If network topology is unstable, SPF throttling calculates SPF scheduling intervals to be longer

until topology becomes stable.

SPF calculations occur at the interval set by the timers throttle spf command. The wait interval

indicates the amount of time to wait until the next SPF calculation occurs. Each wait interval after that

calculation is twice as long as the previous interval until the interval reaches the maximum wait time

specified.

The SPF timing can be better explained using an example. In this example, the start interval is set at

5 milliseconds (ms), initial wait interval at 1000 ms, and maximum wait time at 90,000 ms.

timers spf 5 1000 90000

Figure 8 shows the intervals at which the SPF calculations occur as long as at least one topology change

event is received in a given wait interval.

Figure 8 SPF Calculation Intervals Set by the timers spf Command

Notice that the wait interval between SPF calculations doubles when at least one topology change event

is received during the previous wait interval. After the maximum wait time is reached, the wait interval

remains the same until the topology stabilizes and no event is received in that interval.

If the first topology change event is received after the current wait interval, the SPF calculation is

delayed by the amount of time specified as the start interval. The subsequent wait intervals continue to

follow the dynamic pattern.

If the first topology change event occurs after the maximum wait interval begins, the SPF calculation is

again scheduled at the start interval and subsequent wait intervals are reset according to the parameters

specified in the timers throttle spf command. Notice in Figure 9 that a topology change event was

received after the start of the maximum wait time interval and that the SPF intervals have been reset.

Figure 9 Timer Intervals Reset After Topology Change Event

Nonstop Forwarding for OSPF Version 2

Cisco IOS XR NSF for OSPF Version 2 allows for the forwarding of data packets to continue along

known routes while the routing protocol information is being restored following a failover. With NSF,

peer networking devices do not experience routing flaps. During failover, data traffic is forwarded

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start interval

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through intelligent line cards while the standby Route Processor (RP) assumes control from the failed

RP. The ability of line cards to remain up through a failover and to be kept current with the Forwarding

Information Base (FIB) on the active RP is key to Cisco IOS XR NSF operation.

Routing protocols, such as OSPF, run only on the active RP or DRP and receive routing updates from

their neighbor routers. When an OSPF NSF-capable router performs an RP failover, it must perform two

tasks to resynchronize its link-state database with its OSPF neighbors. First, it must relearn the available

OSPF neighbors on the network without causing a reset of the neighbor relationship. Second, it must

reacquire the contents of the link-state database for the network.

As quickly as possible after an RP failover, the NSF-capable router sends an OSPF NSF signal to

neighboring NSF-aware devices. This signal is in the form of a link-local LSA generated by the

failed-over router. Neighbor networking devices recognize this signal as a cue that the neighbor

relationship with this router should not be reset. As the NSF-capable router receives signals from other

routers on the network, it can begin to rebuild its neighbor list.

After neighbor relationships are re-established, the NSF-capable router begins to resynchronize its

database with all of its NSF-aware neighbors. At this point, the routing information is exchanged

between the OSPF neighbors. After this exchange is completed, the NSF-capable device uses the routing

information to remove stale routes, update the RIB, and update the FIB with the new forwarding

information. OSPF on the router as well as the OSPF neighbors are now fully converged.

Note The standardized IETF version of NSF, known as OSPF graceful restart (RFC 3623) is also supported.

Load Balancing in OSPF Version 2 and OSPFv3

When a router learns multiple routes to a specific network by using multiple routing processes (or

routing protocols), it installs the route with the lowest administrative distance in the routing table.

Sometimes the router must select a route from among many learned by using the same routing process

with the same administrative distance. In this case, the router chooses the path with the lowest cost (or

metric) to the destination. Each routing process calculates its cost differently; the costs may need to be

manipulated to achieve load balancing.

OSPF performs load balancing automatically. If OSPF finds that it can reach a destination through more

than one interface and each path has the same cost, it installs each path in the routing table. The only

restriction on the number of paths to the same destination is controlled by the maximum-paths (OSPF)

command. The default number of maximum paths is 32 for Cisco CRS-1 routers and 16 for

Cisco XR 12000 Series Routers. The range is from 1 to 32 for Cisco CRS-1 routers and 1 to 16 for

Cisco XR 12000 Series Routers.

Graceful Restart for OSPFv3

In the current release, various restart scenarios in the control plane of an IPv6-enabled router can disrupt

data forwarding. The OSPFv3 Graceful Restart feature can preserve the data plane capability in the

following circumstances:

•RP failure, resulting in a switchover to the backup processor

•Planned OSPFv3 process restart, such as software upgrade or downgrade

•Unplanned OSPFv3 process restart, such as a process crash

This feature supports non-stop data forwarding on established routes while the OSPFv3 routing protocol

is restarting. (Therefore, this feature enhances high availability of IPv6 forwarding.)

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Modes of Graceful Restart Operation

The two operational modes that a router can be in for this feature are restart mode and helper mode.

Restart mode occurs when the OSPFv3 process is doing a graceful restart. Helper mode refers to the

neighbor routers that continue to forward traffic on established OSPFv3 routes while OSPFv3 is

restarting on a neighboring router.

Restart Mode

When the OSPFv3 process starts up, it determines whether it must attempt a graceful restart. The

determination is based on whether graceful restart was previously enabled. (OSPFv3 does not attempt a

graceful restart upon the first-time startup of the router.) When OSPFv3 graceful restart is enabled, it

changes the purge timer in the RIB to a non-zero value. See Configuring OSPFv3 Graceful Restart,

page RC-181, for descriptions of how to enable and configure the Graceful Restart feature.

During a graceful restart, the router does not populate OSPFv3 routes in the RIB. It tries to bring up full

adjacencies with the fully-adjacent neighbors that OSPFv3 had before the restart. Eventually, the

OSPFv3 process indicates to the RIB that it has converged either for the purpose of terminating the

graceful restart (for any reason) or because it has completed the graceful restart.

The following are general details about restart mode. More detailed information on behavior and certain

restrictions and requirements appear in the Graceful Restart Requirements and Restrictions section.

•If the OSPFv3 attempts a restart too soon after the most recent restart, the OSPFv3 process is most

likely crashing repeatedly, so the new graceful restart stops running. To control the period between

allowable graceful restarts, use the graceful-restart interval command. A description of how to set

this time period appears in the section Configuring the Minimum Time Required Between Restarts,

page RC-183.

•When OSFPv3 starts a graceful restart with the first interface that comes up, a timer starts running

to limit the duration (or lifetime) of the graceful restart. You can configure this period with the

graceful-restart lifetime command. On each interface that comes up, a grace LSA (type 11) is

flooded to indicate to the neighboring routers that this router is attempting graceful restart. The

neighbors enter into helper mode.

•The designated router and backup designated router check of the hello packet received from the

restarting neighbor is bypassed because it might not be valid.

Helper Mode

Helper mode is enabled by default. When a (helper) router receives a grace LSA (type 11) from a router

that is attempting a graceful restart, the following events occur:

•If helper mode has been disabled through the graceful-restart helper disable command, the router

drops the LSA packet.

•If helper mode is enabled, the router enters helper mode if all of the following conditions are met.

–

The local router itself is not attempting a graceful restart.

–

The local (helping) router has full adjacency with the sending neighbor.

–

The value of lsage (link state age) in the received LSA is less than the requested grace period.

–

The sender of the grace LSA is the same as the originator of the grace LSA.

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•Upon entering helper mode, a router performs its helper function for a specific period of time. This

time period is the lifetime value from the router that is in restart mode—minus the value of lsage in

the received grace LSA. If the graceful restart succeeds in time, the helper’s timer is stopped before

it expires. If the helper’s timer does expire, the adjacency to the restarting router is brought down,

and normal OSPFv3 functionality resumes.

•The dead timer is not honored by the router that is in helper mode.

•A router in helper mode ceases to perform the helper function in any of the following cases:

–

The helper router is able to bring up a FULL adjacency with the restarting router.

–

The local timer for the helper function expires.

Graceful Restart Requirements and Restrictions

The requirements for supporting the Graceful Restart feature include:

•Cooperation of a router’s neighbors during a graceful restart. In relation to the router on which

OSPFv3 is restarting, each router is called a helper.

•All neighbors of the router that does a graceful restart must be capable of doing a graceful restart.

•A graceful restart does not occur upon the first-time startup of a router.

•OSPFv3 neighbor information and database information are not check-pointed.

•An OSPFv3 process rebuilds adjacencies after it restarts.

•To ensure consistent databases after a restart, the OSPFv3 configuration must be identical to the

configuration before the restart. (This requirement applies to self-originated information in the local

database.) A graceful restart can fail if configurations change during the operation. In this case, data

forwarding would be affected. OSPFv3 resumes operation by regenerating all its LSAs and

resynchronizing its database with all its neighbors.

•Although IPv6 FIB tables remain unchanged during a graceful restart, these tables eventually mark

the routes as stale through the use of a holddown timer. Enough time is allowed for the protocols to

rebuild state information and converge.

•The router on which OSPFv3 is restarting must send OSPFv3 hellos within the dead interval of the

process restart. Protocols must be able to retain adjacencies with neighbors before the adjacency

dead timer expires. The default for the dead timer is 40 seconds. If hellos do not arrive on the

adjacency before the dead timer expires, the router takes down the adjacency. The OSPFv3 Graceful

Restart feature does not function properly if the dead timer is configured to be less than the time

required to send hellos after the OSPFv3 process restarts.

•Simultaneous graceful restart sessions on multiple routers are not supported on a single network

segment. If a router determines that multiple routers are in restart mode, it terminates any local

graceful restart operation.

•This feature utilizes the available support for changing the purge time of existing OSPFv3 routes in

the routing information base (RIB). When graceful restart is enabled, the purge timer is set to 90

seconds by default. If graceful restart is disabled, the purge timer setting is 0.

•This feature has an associated grace LSA. This link-scope LSA is type 11.

•According to the RFC, the OSPFv3 process should flush all old, self-originated LSAs during a

restart. With the Graceful Restart feature, however, the router delays this flushing of unknown

self-originated LSAs during a graceful restart. OSPFv3 can learn new information and build new

LSAs to replace the old LSAs. When the delay is over, all old LSAs are flushed.

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•If graceful restart is enabled, the adjacency creation time of all the neighbors is saved in the system

database (SysDB). The purpose for saving the creation time is so that OSPFv3 can use the original

adjacency creation time to display the uptime for that neighbor after the restart.

Multicast-Intact Feature

The multicast-intact feature provides the ability to run multicast routing (PIM) when IGP shortcuts are

configured and active on the router. Both OSPFv2 and IS-IS support the multicast-intact feature.

You can enable multicast-intact in the IGP when multicast routing protocols (PIM) are configured and

IGP shortcuts are configured on the router. IGP shortcuts are MPLS tunnels that are exposed to IGP. The

IGPs routes IP traffic over these tunnels to destinations that are downstream from the egress router of

the tunnel (from an SPF perspective). PIM cannot use IGP shortcuts for propagating PIM joins because

reverse path forwarding (RPF) cannot work across a unidirectional tunnel.

When you enable multicast-intact on an IGP, the IGP publishes a parallel or alternate set of equal-cost

next-hops for use by PIM. These next-hops are called mcast-intact next-hops. The mcast-intact

next-hops have the following attributes:

•They are guaranteed not to contain any IGP shortcuts.

•They are not used for unicast routing but are used only by PIM to look up an IPv4 next-hop to a PIM

source.

•They are not published to the FIB.

•When multicast-intact is enabled on an IGP, all IPv4 destinations that were learned through

link-state advertisements are published with a set equal-cost mcast-intact next-hops to the RIB. This

attribute applies even when the native next-hops have no IGP shortcuts.

•In OSPF, the max-paths (number of equal-cost next-hops) limit is applied separately to the native

and mcast-intact next-hops. The number of equal cost mcast-intact next-hops is the same as that

configured for the native next-hops. (In IS-IS, the behavior is slightly different.)

How to Implement OSPF on Cisco IOS XR Software

This section contains the following procedures:

•Enabling OSPF, page RC-145 (required)

•Configuring Stub and Not-so-Stubby Area Types, page RC-147 (optional)

•Configuring Neighbors for Nonbroadcast Networks, page RC-150 (optional)

•Configuring Authentication at Different Hierarchical Levels for OSPF Version 2, page RC-155

(optional)

•Controlling the Frequency that the Same LSA Is Originated or Accepted for OSPF, page RC-158

(optional)

•Creating a Virtual Link with MD5 Authentication to Area 0 for OSPF, page RC-160 (optional)

•Summarizing Subnetwork LSAs on an OSPF ABR, page RC-164 (optional)

•Redistributing Routes from One IGP into OSPF, page RC-166 (optional)

•Configuring OSPF Shortest Path First Throttling, page RC-170 (optional)

•Configuring Nonstop Forwarding for OSPF Version 2, page RC-173 (optional)

•Configuring OSPF Version 2 for MPLS Traffic Engineering, page RC-175 (optional)

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•Verifying OSPF Configuration and Operation, page RC-180 (optional)

•Configuring OSPFv3 Graceful Restart, page RC-181 (optional)

•Enabling Multicast-Intact for OSPFv2, page RC-186 (optional)

Enabling OSPF

This task explains how to perform the minimum OSPF configuration on your router that is to enable an

OSPF process with a router ID, configure a backbone or nonbackbone area, and then assign one or more

interfaces on which OSPF runs.

Prerequisites

Although you can configure OSPF before you configure an IP address, no OSPF routing occurs until at

least one IP address is configured.

SUMMARY STEPS

1. configure

2. router ospf process-name

router ospfv3 process-name

3. router-id {ipv4-address | interface-type interface-instance}

4. area area-id

5. interface type instance

6. Repeat Step 5 for each interface that use OSPF.

7. log adjacency changes [detail] [enable | disable]

8. end

commit

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DETAILED STEPS

Command or Action Purpose

Step 1 configure

Example:

RP/0/RP0/CPU0:router# configure

Enters global configuration mode.

Step 2 router ospf

process-name

router ospfv3

process-name

Example:

RP/0/RP0/CPU0:router(config)# router ospf 1

RP/0/RP0/CPU0:router(config)# router ospfv3 1

Enables OSPF routing for the specified routing process, and

places the router in router configuration mode.

Enables OSPFv3 routing for the specified routing process,

and places the router in router ospfv3 configuration mode.

Note The process-name argument is any alphanumeric

string no longer than 40 characters.

Step 3 router-id {

ipv4-address

interface-type

interface-instance

}

Example:

RP/0/RP0/CPU0:router(config-ospf)# router-id

192.168.4.3

Configures a router ID for the OSPF process.

Note We recommend using a stable IP address as the

router ID.

Step 4 area

area-id

Example:

RP/0/RP0/CPU0:router(config-ospf)# area 0

Enters area configuration mode and configures an area for

the OSPF process.

•Backbone areas have an area ID of 0.

•Nonbackbone areas have a nonzero area ID.

•The area-id argument can be entered in dotted-decimal

or IPv4 address notation, such as area 1000 or

area 0.0.3.232. However, you must choose one form or

the other for an area. We recommend using the IPv4

address notation.

Step 5 interface

type instance

Example:

RP/0/RP0/CPU0:router(config-ospf-ar)# interface

POS 0/1/0/3

Enters interface configuration mode and associates one or

more interfaces for the area configured in Step 4.

Step 6 Repeat Step 5 for each interface that uses OSPF. —

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How to Implement OSPF on Cisco IOS XR Software

RC-147

Cisco IOS XR Routing Configuration Guide

Configuring Stub and Not-so-Stubby Area Types

This task explains how to configure the stub area and the NSSA for OSPF.

SUMMARY STEPS

1. configure

2. router ospf process-name

router ospfv3 process-name

3. router-id {ipv4-address | interface-type interface-instance}

4. area area-id

5. stub [no-summary]

nssa [no-redistribution] [default-information-originate] [no-summary]

Step 7 log adjacency changes [detail] [enable |

disable]

Example:

RP/0/RP0/CPU0:router(config-ospf-ar-if)# log

adjacency changes detail

(Optional) Requests notification of neighbor changes.

•By default, this feature is enabled.

•The messages generated by neighbor changes are

considered notifications, which are categorized as

severity Level 5 in the logging console command. The

logging console command controls which severity

level of messages are sent to the console. By default, all

severity level messages are sent.

Step 8 end

commit

Example:

RP/0/RP0/CPU0:router(config-ospf-ar-if)# end

RP/0/RP0/CPU0:router(config-ospf-ar-if)# commit

Saves configuration changes.

•When you issue the end command, the system prompts

you to commit changes:

Uncommitted changes found, commit them before

exiting(yes/no/cancel)?

[cancel]:

–

Entering yes saves configuration changes to the

running configuration file, exits the configuration

session, and returns the router to EXEC mode.

–

Entering no exits the configuration session and

returns the router to EXEC mode without

committing the configuration changes.

–

Entering cancel leaves the router in the current

configuration session without exiting or

committing the configuration changes.

•Use the commit command to save the configuration

changes to the running configuration file and remain

within the configuration session.

Command or Action Purpose

Implementing OSPF on Cisco IOS XR Software

How to Implement OSPF on Cisco IOS XR Software

RC-148

Cisco IOS XR Routing Configuration Guide

6. stub

nssa

7. default-cost cost

8. end

commit

9. Repeat this task on all other routers in the stub area or NSSA.

DETAILED STEPS

Command or Action Purpose

Step 1 configure

Example:

RP/0/RP0/CPU0:router# configure

Enters global configuration mode.

Step 2 router ospf

process-name

router ospfv3

process-name

Example:

RP/0/RP0/CPU0:router(config)# router ospf 1

RP/0/RP0/CPU0:router(config)# router ospfv3 1

Enables OSPF routing for the specified routing process, and

places the router in router configuration mode.

Enables OSPFv3 routing for the specified routing process,

and places the router in router ospfv3 configuration mode.

Note The process-name argument is any alphanumeric

string no longer than 40 characters.

Step 3 router-id {

ipv4-address

interface-type

interface-instance

}

Example:

RP/0/RP0/CPU0:router(config-ospf)# router-id

192.168.4.3

Configures a router ID for the OSPF process.

Note We recommend using a stable IP address as the

router ID.

Step 4 area

area-id

Example:

RP/0/RP0/CPU0:router(config-ospf)# area 1

Enters area configuration mode and configures a

nonbackbone area for the OSPF process.

•The area-id argument can be entered in dotted-decimal

or IPv4 address notation, such as area 1000 or

area 0.0.3.232. However, you must choose one form or

the other for an area. We recommend using the IPv4

address notation.

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Cisco IOS XR Routing Configuration Guide

Step 5 stub [no-summary]

nssa [no-redistribution]

[default-information-originate] [no-summary]

Example:

RP/0/RP0/CPU0:router(config-ospf-ar)# stub no

summary

RP/0/RP0/CPU0:router(config-ospf-ar)# nssa

no-redistribution

Defines the nonbackbone area as a stub area.

•See the “Configuring Stub and Not-so-Stubby Area

Types” section on page RC-147.

•Specify the no-summary keyword to further reduce the

number of LSAs sent into a stub area. This keyword

prevents the ABR from sending summary link-state

advertisements (Type 3) in the stub area.

Defines an area as an NSSA.

•See the “Configuring Stub and Not-so-Stubby Area

Types” section on page RC-147.

Step 6 stub

nssa

Example:

RP/0/RP0/CPU0:router(config-ospf-ar)# stub

RP/0/RP0/CPU0:router(config-ospf-ar)# nssa

(Optional) Turns off the options configured for stub and

NSSA areas.

•If you configured the stub and NSSA areas using the

optional keywords (no-summary, no-redistribution,

default-information-originate, and no-summary) in

Step 5, you must now reissue the stub and nssa

commands without the keywords—rather than using

the no form of the command.

•For example, the no nssa

default-information-originate form of the command

changes the NSSA area into a normal area that

inadvertently brings down the existing adjacencies in

that area.

Step 7 default-cost

cost

Example:

RP/0/RP0/CPU0:router(config-ospf-ar)#

default-cost 15

(Optional) Specifies a cost for the default summary route

sent into a stub area or an NSSA.

•Use this command only on ABRs attached to the NSSA.

Do not use it on any other routers in the area.

•The default cost is 1.

Command or Action Purpose

Implementing OSPF on Cisco IOS XR Software

How to Implement OSPF on Cisco IOS XR Software

RC-150

Cisco IOS XR Routing Configuration Guide

Configuring Neighbors for Nonbroadcast Networks

This task explains how to configure neighbors for a nonbroadcast network. This task is optional.

Prerequisites

Configuring NBMA networks as either broadcast or nonbroadcast assumes that there are virtual circuits

from every router to every other router or a fully meshed network.

SUMMARY STEPS

1. configure

2. router ospf process-name

router ospfv3 process-name

3. router-id {ipv4-address | interface-type interface-instance}

4. area area-id

5. network {broadcast | non-broadcast | {point-to-multipoint [non-broadcast] | point-to-point}}

6. dead-interval seconds

7. hello-interval seconds

8. interface type number

Step 8 end

commit

Example:

RP/0/RP0/CPU0:router(config-ospf-ar)# end

RP/0/RP0/CPU0:router(config-ospf-ar)# commit

Saves configuration changes.

•When you issue the end command, the system prompts

you to commit changes:

Uncommitted changes found, commit them before

exiting(yes/no/cancel)?

[cancel]:

–

Entering yes saves configuration changes to the

running configuration file, exits the configuration

session, and returns the router to EXEC mode.

–

Entering no exits the configuration session and

returns the router to EXEC mode without

committing the configuration changes.

–

Entering cancel leaves the router in the current

configuration session without exiting or

committing the configuration changes.

•Use the commit command to save the configuration

changes to the running configuration file and remain

within the configuration session.

Step 9 Repeat this task on all other routers in the stub area or

NSSA.

—

Command or Action Purpose

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How to Implement OSPF on Cisco IOS XR Software

RC-151

Cisco IOS XR Routing Configuration Guide

9. neighbor ip-address [priority number] [poll-interval seconds] [cost number]

neighbor ipv6-link-local-address [priority number] [poll-interval seconds] [cost number]

[database-filter [all]]

10. Repeat Step 9 for all neighbors on the interface.

11. exit

12. interface type instance

13. neighbor ip-address [priority number] [poll-interval seconds][cost number] [database-filter

[all]]

neighbor ipv6-link-local-address [priority number] [poll-interval seconds][cost number]

[database-filter [all]]

14. Repeat Step 13 for all neighbors on the interface.

15. end

commit

DETAILED STEPS

Command or Action Purpose

Step 1 configure

Example:

RP/0/RP0/CPU0:router# configure

Enters global configuration mode.

Step 2 router ospf

process-name

router ospfv3

process-name

Example:

RP/0/RP0/CPU0:router(config)# router ospf 1

RP/0/RP0/CPU0:router(config)# router ospfv3 1

Enables OSPF routing for the specified routing process, and

places the router in router configuration mode.

Enables OSPFv3 routing for the specified routing process,

and places the router in router ospfv3 configuration mode.

Note The process-name argument is any alphanumeric

string no longer than 40 characters.

Step 3 router-id {

ipv4-address

interface-type

interface-instance

}

Example:

RP/0/RP0/CPU0:router(config-ospf)# router-id

192.168.4.3

Configures a router ID for the OSPF process.

Note We recommend using a stable IP address as the

router ID.

Step 4 area

area-id

Example:

RP/0/RP0/CPU0:router(config-ospf)# area 0

Enters area configuration mode and configures an area for

the OSPF process.

•This example configures a backbone area.

•The area-id argument can be entered in dotted-decimal

or IPv4 address notation, such as area 1000 or

area 0.0.3.232. However, you must choose one form or

the other for an area. We recommend using the IPv4

address notation.

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Cisco IOS XR Routing Configuration Guide

Step 5 network {broadcast | non-broadcast |

{point-to-multipoint [non-broadcast] |

point-to-point}}

Example:

RP/0/RP0/CPU0:router(config-ospf-ar)# network

non-broadcast

Configures the OSPF network type to a type other than the

default for a given medium.

•The example sets the network type to NBMA.

Step 6 dead-interval

seconds

Example:

RP/0/RP0/CPU0:router(config-ospf-ar)#

dead-interval 40

(Optional) Sets the time to wait for a hello packet from a

neighbor before declaring the neighbor down.

Step 7 hello-interval

seconds

Example:

RP/0/RP0/CPU0:router(config-ospf-ar)#

hello-interval 10

(Optional) Specifies the interval between hello packets that

OSPF sends on the interface.

Step 8 interface

type instance

Example:

RP/0/RP0/CPU0:router(config-ospf-ar)# interface

POS 0/2/0/0

Enters interface configuration mode and associates one or

more interfaces for the area configured in Step 4.

•In this example, the interface inherits the nonbroadcast

network type and the hello and dead intervals from the

areas because the values are not set at the interface

level.

Command or Action Purpose

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How to Implement OSPF on Cisco IOS XR Software

RC-153

Cisco IOS XR Routing Configuration Guide

Step 9 neighbor

ip-address

[priority

number

]

[poll-interval

seconds

][cost

number

]

neighbor

ipv6-link-local-address

[priority

number

] [poll-interval

seconds

][cost

number

]

[database-filter [all]]

Example:

RP/0/RP0/CPU0:router(config-ospf-ar-if)#

neighbor 10.20.20.1 priority 3 poll-interval 15

RP/0/RP0/CPU0:router(config-ospf-ar-if)#

neighbor fe80::3203:a0ff:fe9d:f3fe

Configures the IPv4 address of OSPF neighbors

interconnecting to nonbroadcast networks.

Configures the link-local IPv6 address of OSPFv3

neighbors.

•The ipv6-link-local-address must be in the form that is

specified in RFC 2373. The address is specified in

hexadecimal using 16-bit values between colons.

•The priority keyword notifies the router that this

neighbor is eligible to become a DR or BDR. The

priority value should match the actual priority setting

on the neighbor router. The neighbor priority default

value is 0. This keyword does not apply to

point-to-multipoint interfaces.

•The poll-interval keyword does not apply to

point-to-multipoint interfaces. RFC 1247 recommends

that this value be much larger than the hello interval.

The default is 120 seconds (2 minutes).

•Neighbors with no specific cost configured assumes the

cost of the interface, based on the cost command. On

point-to-multipoint interfaces, cost number is the only

keyword and argument combination that works. The

cost keyword does not apply to NBMA networks.

•The database-filter keyword filters outgoing LSAs to

an OSPF neighbor. If you specify the all keyword,

incoming and outgoing LSAs are filtered. Use with

extreme caution because filtering might cause the

routing topology to be seen as entirely different

between two neighbors, resulting in black-holing of

data traffic or routing loops.

Step 10 Repeat Step 9 for all neighbors on the interface. —

Step 11 exit

Example:

RP/0/RP0/CPU0:router(config-ospf-ar-if)# exit

Enters area configuration mode.

Step 12 interface

type instance

Example:

RP/0/RP0/CPU0:router(config-ospf-ar)# interface

POS 0/3/0/1

Enters interface configuration mode and associates one or

more interfaces for the area configured in Step 4.

•In this example, the interface inherits the nonbroadcast

network type and the hello and dead intervals from the

areas because the values are not set at the interface

level.

Command or Action Purpose

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Cisco IOS XR Routing Configuration Guide

Step 13 neighbor

ip-address

[priority

number

]

[poll-interval

seconds

][cost

number

]

[database-filter [all]]

neighbor

ipv6-link-local-address

[priority

number

] [poll-interval

seconds

][cost

number

]

[database-filter [all]]

Example:

RP/0/RP0/CPU0:router(config-ospf-ar)# neighbor

10.34.16.6

RP/0/RP0/CPU0:router(config-ospf-ar)# neighbor

fe80::3203:a0ff:fe9d:f3f

Configures the IPv4 address of OSPF neighbors

interconnecting to nonbroadcast networks.

Configures the link-local IPv6 address of OSPFv3

neighbors.

•The ipv6-link-local-address argument must be in the

form documented in RFC 2373 in which the address is

specified in hexadecimal using 16-bit values between

colons.

•The priority keyword notifies the router that this

neighbor is eligible to become a DR or BDR. The

priority value should match the actual priority setting

on the neighbor router. The neighbor priority default

value is zero. This keyword does not apply to

point-to-multipoint interfaces.

•The poll-interval keyword does not apply to

point-to-multipoint interfaces. RFC 1247 recommends

that this value be much larger than the hello interval.

The default is 120 seconds (2 minutes).

•Neighbors with no specific cost configured assumes the

cost of the interface, based on the cost command. On

point-to-multipoint interfaces, cost number is the only

keyword and argument combination that works. The

cost keyword does not apply to NBMA networks.

•The database-filter keyword filters outgoing LSAs to

an OSPF neighbor. If you specify the all keyword,

incoming and outgoing LSAs are filtered. Use with

extreme caution since filtering may cause the routing

topology to be seen as entirely different between two

neighbors, resulting in ‘black-holing’ or routing loops.

Command or Action Purpose

Implementing OSPF on Cisco IOS XR Software

How to Implement OSPF on Cisco IOS XR Software

RC-155

Cisco IOS XR Routing Configuration Guide

Configuring Authentication at Different Hierarchical Levels for OSPF Version 2

This task explains how to configure MD5 (secure) authentication on the OSPF router process, configure

one area with plain text authentication, and then apply one interface with clear text (null) authentication.

Note Authentication configured at the interface level overrides authentication configured at the area level and

the router process level. If an interface does not have authentication specifically configured, the interface

inherits the authentication parameter value from a higher hierarchical level. See the “OSPF Hierarchical

CLI and CLI Inheritance” section on page RC-131 for more information about hierarchy and inheritance.

Prerequisites

If you choose to configure authentication, you must first decide whether to configure plain text or MD5

authentication, and whether the authentication applies to all interfaces in a process, an entire area, or

specific interfaces. See the “Route Authentication Methods for OSPF Version 2” section on

page RC-135 for information about each type of authentication and when you should use a specific

method for your network.

SUMMARY STEPS

1. configure

2. router ospf process-name

3. router-id {ipv4-address | interface-type interface-instance}

4. authentication [message-digest | null]

Step 14 Repeat Step 13 for all neighbors on the interface. —

Step 15 end

commit

Example:

RP/0/RP0/CPU0:router(config-ospf-ar)# end

RP/0/RP0/CPU0:router(config-ospf-ar)# commit

Saves configuration changes.

•When you issue the end command, the system prompts

you to commit changes:

Uncommitted changes found, commit them before

exiting(yes/no/cancel)?

[cancel]:

–

Entering yes saves configuration changes to the

running configuration file, exits the configuration

session, and returns the router to EXEC mode.

–

Entering no exits the configuration session and

returns the router to EXEC mode without

committing the configuration changes.

–

Entering cancel leaves the router in the current

configuration session without exiting or

committing the configuration changes.

•Use the commit command to save the configuration

changes to the running configuration file and remain

within the configuration session.

Command or Action Purpose

Implementing OSPF on Cisco IOS XR Software

How to Implement OSPF on Cisco IOS XR Software

RC-156

Cisco IOS XR Routing Configuration Guide

5. message-digest-key key-id md5 {key | clear key | encrypted key}

6. area area-id

7. interface type instance

8. Repeat Step 7 for each interface that must communicate, using the same authentication.

9. exit

10. area area-id

11. authentication [message-digest | null]

12. interface type instance

13. Repeat Step 7 for each interface that must communicate, using the same authentication.

14. interface type instance

15. authentication [message-digest | null]

16. end

commit

DETAILED STEPS

Command or Action Purpose

Step 1 configure

Example:

RP/0/RP0/CPU0:router# configure

Enters global configuration mode.

Step 2 router ospf

process-name

Example:

RP/0/RP0/CPU0:router(config)# router ospf 1

Enables OSPF routing for the specified routing process, and

places the router in router configuration mode.

Note The process-name argument is any alphanumeric

string no longer than 40 characters.

Step 3 router-id {

ipv4-address

interface-type

interface-instance

}

Example:

RP/0/RP0/CPU0:router(config-ospf)# router-id

192.168.4.3

Configures a router ID for the OSPF process.

Step 4 authentication [message-digest | null]

Example:

RP/0/RP0/CPU0:router(config-ospf)#

authentication message-digest

Enables MD5 authentication for the OSPF process.

•This authentication type applies to the entire router

process unless overridden by a lower hierarchical level

such as the area or interface.

Step 5 message-digest-key

key-id

md5 {

key

| clear

key

| encrypted

key

}

Example:

RP/0/RP0/CPU0:router(config-ospf)#

message-digest-key 4 md5 yourkey

Specifies the MD5 authentication key for the OSPF process.

•The neighbor routers must have the same key identifier.

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How to Implement OSPF on Cisco IOS XR Software

RC-157

Cisco IOS XR Routing Configuration Guide

Step 6 area

area-id

Example:

RP/0/RP0/CPU0:router(config-ospf)# area 0

Enters area configuration mode and configures a backbone

area for the OSPF process.

Step 7 interface

type instance

Example:

RP/0/RP0/CPU0:router(config-ospf-ar)# interface

POS 0/1/0/3

Enters interface configuration mode and associates one or

more interfaces to the backbone area.

•All interfaces inherit the authentication parameter

values specified for the OSPF process (Step 4, Step 5,

and Step 6).

Step 8 Repeat Step 7 for each interface that must

communicate, using the same authentication.

—

Step 9 exit

Example:

RP/0/RP0/CPU0:router(config-ospf-ar)# exit

Enters area OSPF configuration mode.

Step 10 area

area-id

Example:

RP/0/RP0/CPU0:router(config-ospf)# area 1

Enters area configuration mode and configures a

nonbackbone area 1 for the OSPF process.

•The area-id argument can be entered in dotted-decimal

or IPv4 address notation, such as area 1000 or

area 0.0.3.232. However, you must choose one form or

the other for an area. We recommend using the IPv4

address notation.

Step 11 authentication [message-digest | null]

Example:

RP/0/RP0/CPU0:router(config-ospf-ar)#

authentication

Enables Type 1 (plain text) authentication that provides no

security.

•The example specifies plain text authentication (by not

specifying a keyword). Use the authentication-key

interface command to specify the plain text password.

Step 12 interface

type instance

Example:

RP/0/RP0/CPU0:router(config-ospf-ar)# interface

POS 0/1/0/0

Enters interface configuration mode and associates one or

more interfaces to the nonbackbone area 1 specified in

Step 7.

•All interfaces configured inherit the authentication

parameter values configured for area 1.

Step 13 Repeat Step 12 for each interface that must

communicate, using the same authentication.

—

Step 14 interface

type instance

Example:

RP/0/RP0/CPU0:router(config-ospf-ar)# interface

POS 0/3/0/0

Enters interface configuration mode and associates one or

more interfaces to a different authentication type.

Command or Action Purpose

Implementing OSPF on Cisco IOS XR Software

How to Implement OSPF on Cisco IOS XR Software

RC-158

Cisco IOS XR Routing Configuration Guide

Controlling the Frequency that the Same LSA Is Originated or Accepted for

OSPF

This task explains how to tune the convergence time of OSPF routes in the routing table when many

LSAs need to be flooded in a very short time interval.

SUMMARY STEPS

1. configure

2. router ospf process-name

router ospfv3 process-name

3. router-id {ipv4-address | interface-type interface-instance}

4. Do Step 5, Step 6 or both to control the frequency that the same LSA is originated or accepted.

5. timers lsa gen-interval seconds

6. timers lsa min-arrival seconds

7. timers lsa group-pacing seconds

8. end

commit

Step 15 authentication [message-digest | null]

Example:

RP/0/RP0/CPU0:router(config-ospf-ar-if)#

authentication null

Specifies no authentication on POS interface 0/3/0/0,

overriding the plain text authentication specified for area 1.

•By default, all of the interfaces configured in the same

area inherit the same authentication values of the area.

Step 16 end

commit

Example:

RP/0/RP0/CPU0:router(config-ospf-ar-if)# end

RP/0/RP0/CPU0:router(config-ospf-ar-if)# commit

Saves configuration changes.

•When you issue the end command, the system prompts

you to commit changes:

Uncommitted changes found, commit them before

exiting(yes/no/cancel)?

[cancel]:

–

Entering yes saves configuration changes to the

running configuration file, exits the configuration

session, and returns the router to EXEC mode.

–

Entering no exits the configuration session and

returns the router to EXEC mode without

committing the configuration changes.

–

Entering cancel leaves the router in the current

configuration session without exiting or

committing the configuration changes.

•Use the commit command to save the configuration

changes to the running configuration file and remain

within the configuration session.

Command or Action Purpose

Implementing OSPF on Cisco IOS XR Software

How to Implement OSPF on Cisco IOS XR Software

RC-159

Cisco IOS XR Routing Configuration Guide

DETAILED STEPS

Command or Action Purpose

Step 1 configure

Example:

RP/0/RP0/CPU0:router# configure

Enters global configuration mode.

Step 2 router ospf

process-name

router ospfv3

process-name

Example:

RP/0/RP0/CPU0:router(config)# router ospf 1

RP/0/RP0/CPU0:router(config)# router ospfv3 1

Enables OSPF routing for the specified routing process, and

places the router in router configuration mode.

Enables OSPFv3 routing for the specified routing process,

and places the router in router ospfv3 configuration mode.

Note The process-name argument is any alphanumeric

string no longer than 40 characters.

Step 3 router-id {

ipv4-address

interface-type

interface-instance

}

Example:

RP/0/RP0/CPU0:router(config-ospf)# router-id

192.168.4.3

Configures a router ID for the OSPF process.

Note We recommend using a stable IP address as the

router ID.

Step 4 Perform Step 5 or Step 6 or both to control the

frequency that the same LSA is originated or accepted.

—

Step 5 timers lsa gen-interval

seconds

Example:

RP/0/RP0/CPU0:router(config-ospf)# timers lsa

gen-interval 10

Changes the minimum interval between the same OSPF

LSAs that the router originates.

•The default is 5 seconds for both OSPF and OSPFv3.

Step 6 timers lsa min-arrival

seconds

Example:

RP/0/RP0/CPU0:router(config-ospf)# timers lsa

min-arrival 2

Limits the frequency that new processes of any particular

OSPF Version 2 LSA can be accepted during flooding.

•The default is 1 second.

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Cisco IOS XR Routing Configuration Guide

Creating a Virtual Link with MD5 Authentication to Area 0 for OSPF

This task explains how to create a virtual link to your backbone (area 0) and apply MD5 authentication.

You must perform the steps described on both ABRs, one at each end of the virtual link. To understand

virtual links, see the “Virtual Link and Transit Area for OSPF” section on page RC-138.

Note After you explicitly configure area parameter values, they are inherited by all interfaces bound to that

area—unless you override the values and configure them explicitly for the interface. An example is

provided in the “Virtual Link Configured with MD5 Authentication for OSPF Version 2: Example”

section on page RC-192.

Prerequisites

Meet the following prerequisites before you create a virtual link with MD5 authentication to area 0:

•Have the router ID of the neighbor router at the opposite end of the link to configure the local router.

You can use the show ospf or show ospfv3 command on the remote end to get its router ID.

Step 7 timers lsa group-pacing

seconds

Example:

RP/0/RP0/CPU0:router(config-ospf)# timers lsa

group-pacing 1000

Changes the interval at which OSPF link-state LSAs are

collected into a group for flooding. The default is 240

seconds.

Step 8 end

commit

Example:

RP/0/RP0/CPU0:router(config-ospf)# end

RP/0/RP0/CPU0:router(config-ospf)# commit

Saves configuration changes.

•When you issue the end command, the system prompts

you to commit changes:

Uncommitted changes found, commit them before

exiting(yes/no/cancel)?

[cancel]:

–

Entering yes saves configuration changes to the

running configuration file, exits the configuration

session, and returns the router to EXEC mode.

–

Entering no exits the configuration session and

returns the router to EXEC mode without

committing the configuration changes.

–

Entering cancel leaves the router in the current

configuration session without exiting or

committing the configuration changes.

•Use the commit command to save the configuration

changes to the running configuration file and remain

within the configuration session.

Command or Action Purpose

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•For a virtual link to be successful, you need a stable router ID at each end of the virtual link. You

do not want them to be subject to change, which could happen if they are assigned by default (See

the “OSPF Process and Router ID” section on page RC-134 for an explanation of how the router ID

is determined.) Therefore, we recommend that you perform one of the following tasks before

configuring a virtual link:

–

Use the router-id command to set the router ID. This strategy is preferable.

–

Configure a loopback interface so that the router has a stable router ID.

•Before configuring your virtual link for OSPF Version 2, you must decide whether to configure plain

text authentication, MD5 authentication, or no authentication (which is the default). Your decision

determines whether you need to perform additional tasks related to authentication.

Note If you decide to configure plain text authentication or no authentication, see the authentication

command provided in the OSPF Commands on Cisco IOS XR Software module in the Cisco IOS XR

Routing Command Reference.

SUMMARY STEPS

1. show ospf [process-name]

show ospfv3 [process-name]

2. configure

3. router ospf process-name

router ospfv3 process-name

4. router-id {ipv4-address | interface-type interface-instance}

5. area area-id

6. virtual link router-id

7. authentication message-digest

8. message-digest-key key-id md5 {key | clear key | encrypted key}

9. Repeat all of the steps in this task on the ABR that is at the other end of the virtual link. Specify the

same key ID and key that you specified for the virtual link on this router.

10. end

commit

11. show ospf [process-name] [area-id] virtual-links

show ospfv3 [process-name] virtual-links

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DETAILED STEPS

Command or Action Purpose

Step 1 show ospf [

process-name

]

show ospfv3 [

process-name

]

Example:

RP/0/RP0/CPU0:router# show ospf

RP/0/RP0/CPU0:router# show ospfv3

(Optional) Displays general information about OSPF

routing processes.

•The output displays the router ID of the local router.

You need this router ID to configure the other end of

the link.

Step 2 configure

Example:

RP/0/RP0/CPU0:router# configure

Enters global configuration mode.

Step 3 router ospf

process-name

router ospfv3

process-name

Example:

RP/0/RP0/CPU0:router(config)# router ospf 1

RP/0/RP0/CPU0:router(config)# router ospfv3 1

Enables OSPF routing for the specified routing process, and

places the router in router configuration mode.

Enables OSPFv3 routing for the specified routing process,

and places the router in router ospfv3 configuration mode.

Note The process-name argument is any alphanumeric

string no longer than 40 characters.

Step 4 router-id {

ipv4-address

interface-type

interface-instance

}

Example:

RP/0/RP0/CPU0:router(config-ospf)# router-id

192.168.4.3

Configures a router ID for the OSPF process.

Note We recommend using a stable IPv4 address as the

router ID.

Step 5 area

area-id

Example:

RP/0/RP0/CPU0:router(config-ospf)# area 1

Enters area configuration mode and configures a

nonbackbone area for the OSPF process.

•The area-id argument can be entered in dotted-decimal

or IPv4 address notation, such as area 1000 or

area 0.0.3.232. However, you must choose one form or

the other for an area. We recommend using the IPv4

address notation.

Step 6 virtual-link

router-id

Example:

RP/0/RP0/CPU0:router(config-ospf-ar)# virtual

link 10.3.4.5

Defines an OSPF virtual link.

•See the “Virtual Link and Transit Area for OSPF”

section on page RC-138.

Step 7 authentication message-digest

Example:

RP/0/RP0/CPU0:router(config-ospf-ar-vl)#

authentication message-digest

Selects MD5 authentication for this virtual link.

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Cisco IOS XR Routing Configuration Guide

Step 8 message-digest-key

key-id

md5 {

key

| clear

key

| encrypted

key

}

Example:

RP/0/RP0/CPU0:router(config-ospf-ar-vl)#

message-digest-key 4 md5 yourkey

Defines an OSPF virtual link.

•See the “Virtual Link and Transit Area for OSPF”

section on page RC-138 to understand a virtual link.

•The key-id argument is a number in the range from 1 to

255. The key argument is an alphanumeric string of up

to 16 characters. The routers at both ends of the virtual

link must have the same key identifier and key to be

able to route OSPF traffic.

•The authentication-key key command is not supported

for OSPFv3.

•Once the key is encrypted it must remain encrypted.

Step 9 Repeat all of the steps in this task on the ABR that is

at the other end of the virtual link. Specify the same

key ID and key that you specified for the virtual link

on this router.

—

Step 10 end

commit

Example:

RP/0/RP0/CPU0:router(config-ospf-ar-vl)# end

RP/0/RP0/CPU0:router(config-ospf-ar-vl)# commit

Saves configuration changes.

•When you issue the end command, the system prompts

you to commit changes:

Uncommitted changes found, commit them before

exiting(yes/no/cancel)?

[cancel]:

–

Entering yes saves configuration changes to the

running configuration file, exits the configuration

session, and returns the router to EXEC mode.

–

Entering no exits the configuration session and

returns the router to EXEC mode without

committing the configuration changes.

–

Entering cancel leaves the router in the current

configuration session without exiting or

committing the configuration changes.

•Use the commit command to save the configuration

changes to the running configuration file and remain

within the configuration session.

Step 11 show ospf [

process-name

] [

area-id

]

virtual-links

show ospfv3 [

process-name

] virtual-links

Example:

RP/0/RP0/CPU0:router# show ospf 1 2

virtual-links

RP/0/RP0/CPU0:router# show ospfv3 1

virtual-links

(Optional) Displays the parameters and the current state of

OSPF virtual links.

Command or Action Purpose

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Cisco IOS XR Routing Configuration Guide

Examples

In the following example, the show ospfv3 virtual links EXEC command verifies that the OSPF_VL0

virtual link to the OSPFv3 neighbor is up, the ID of the virtual link interface is 2, and the IPv6 address

of the virtual link endpoint is 2003:3000::1.

RP/0/RP0/CPU0:router# show ospfv3 virtual-links

Virtual Links for OSPFv3 1

Virtual Link OSPF_VL0 to router 10.0.0.3 is up

Interface ID 2, IPv6 address 2003:3000::1

Run as demand circuit

DoNotAge LSA allowed.

Transit area 0.1.20.255, via interface POS 0/1/0/1, Cost of using 2

Transmit Delay is 5 sec, State POINT_TO_POINT,

Timer intervals configured, Hello 10, Dead 40, Wait 40, Retransmit 5

Hello due in 00:00:02

Adjacency State FULL (Hello suppressed)

Index 0/2/3, retransmission queue length 0, number of retransmission 1

First 0(0)/0(0)/0(0) Next 0(0)/0(0)/0(0)

Last retransmission scan length is 1, maximum is 1

Last retransmission scan time is 0 msec, maximum is 0 msec

Check for lines:

Virtual Link OSPF_VL0 to router 10.0.0.3 is up

Adjacency State FULL (Hello suppressed)

State is up and Adjacency State is FULL

Summarizing Subnetwork LSAs on an OSPF ABR

If you configured two or more subnetworks when you assigned your IP addresses to your interfaces, you

might want the software to summarize (aggregate) into a single LSA all of the subnetworks that the local

area advertises to another area. Such summarization would reduce the number of LSAs and thereby

conserve network resources. This summarization is known as interarea route summarization. It applies

to routes from within the autonomous system. It does not apply to external routes injected into OSPF by

way of redistribution.

This task configures OSPF to summarize subnetworks into one LSA, by specifying that all subnetworks

that fall into a range are advertised together. This task is performed on an ABR only.

SUMMARY STEPS

1. configure

2. router ospf process-name

router ospfv3 process-name

3. router-id {ipv4-address | interface-type interface-instance}

4. area area-id

5. range ip-address mask [advertise | not-advertise]

range ipv6-prefix/prefix-length [advertise | not-advertise]

6. interface type instance

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7. end

commit

DETAILED STEPS

Command or Action Purpose

Step 1 configure

Example:

RP/0/RP0/CPU0:router# configure

Enters global configuration mode.

Step 2 router ospf

process-name

router ospfv3

process-name

Example:

RP/0/RP0/CPU0:router(config)# router ospf 1

RP/0/RP0/CPU0:router(config)# router ospfv3 1

Enables OSPF routing for the specified routing process, and

places the router in router configuration mode.

Enables OSPFv3 routing for the specified routing process,

and places the router in router ospfv3 configuration mode.

Note The process-name argument is any alphanumeric

string no longer than 40 characters.

Step 3 router-id {

ipv4-address

interface-type

interface-instance

}

Example:

RP/0/RP0/CPU0:router(config-ospf)# router-id

192.168.4.3

Configures a router ID for the OSPF process.

Note We recommend using a stable IPv4 address as the

router ID.

Step 4 area

area-id

Example:

RP/0/RP0/CPU0:router(config-ospf)# area 0

Enters area configuration mode and configures a

nonbackbone area for the OSPF process.

•The area-id argument can be entered in dotted-decimal

or IPv4 address notation, such as area 1000 or

area 0.0.3.232. However, you must choose one form or

the other for an area. We recommend using the IPv4

address notation.

Step 5 range

ip-address mask

[advertise |

not-advertise]

range

ipv6-prefix

prefix-length

[advertise |

not-advertise]

Example:

RP/0/RP0/CPU0:router(config-ospf-ar)# range

192.168.0.0 255.255.0.0 advertise

Example:

RP/0/RP0/CPU0:router(config-ospf-ar)# range

4004:f000::/32 advertise

Consolidates and summarizes OSPF routes at an area

boundary.

•The advertise keyword causes the software to advertise

the address range of subnetworks in a Type 3 summary

LSA.

•The not-advertise keyword causes the software to

suppress the Type 3 summary LSA, and the

subnetworks in the range remain hidden from other

areas.

•In the first example, all subnetworks for network

192.168.0.0 are summarized and advertised by the

ABR into areas outside the backbone.

•In the second example, two or more IPv4 interfaces are

covered by a 192.x.x network.

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Cisco IOS XR Routing Configuration Guide

Redistributing Routes from One IGP into OSPF

This task redistributes routes from an IGP (could be a different OSPF process) into OSPF.

Prerequisites

For information about configuring routing policy, see the Implementing Routing Policy on Cisco IOS XR

Software module.

SUMMARY STEPS

1. configure

2. router ospf process-name

router ospfv3 process-name

3. router-id {ipv4-address | interface-type interface-instance}

4. redistribute protocol [process-id] {level-1 | level-1-2 | level-2} [metric metric-value] [metric-type

type-value] [match {internal | external [1 | 2} | nssa-external [1 | 2}] [tag tag-value] [route-map

map-tag | policy policy-tag]

Step 6 interface

type

instance

Example:

RP/0/RP0/CPU0:router(config-ospf-ar)# interface

POS 0/2/0/3

Enters interface configuration mode and associates one or

more interfaces to the area.

Step 7 end

commit

Example:

RP/0/RP0/CPU0:router(config-ospf-ar)# end

RP/0/RP0/CPU0:router(config-ospf-ar)# commit

Saves configuration changes.

•When you issue the end command, the system prompts

you to commit changes:

Uncommitted changes found, commit them before

exiting(yes/no/cancel)?

[cancel]:

–

Entering yes saves configuration changes to the

running configuration file, exits the configuration

session, and returns the router to EXEC mode.

–

Entering no exits the configuration session and

returns the router to EXEC mode without

committing the configuration changes.

–

Entering cancel leaves the router in the current

configuration session without exiting or

committing the configuration changes.

•Use the commit command to save the configuration

changes to the running configuration file and remain

within the configuration session.

Command or Action Purpose

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5. summary-prefix address mask [not-advertise] [tag tag]

summary-prefix ipv6-prefix/prefix-length [not-advertise] [tag tag]

6. end

commit

DETAILED STEPS

Command or Action Purpose

Step 1 configure

Example:

RP/0/RP0/CPU0:router# configure

Enters global configuration mode.

Step 2 router ospf

process-name

router ospfv3

process-name

Example:

RP/0/RP0/CPU0:router(config)# router ospf 1

RP/0/RP0/CPU0:router(config)# router ospfv3 1

Enables OSPF routing for the specified routing process, and

places the router in router configuration mode.

Enables OSPFv3 routing for the specified routing process,

and places the router in router ospfv3 configuration mode.

Note The process-name argument is any alphanumeric

string no longer than 40 characters.

Step 3 router-id {

ipv4-address

interface-type

interface-instance

}

Example:

RP/0/RP0/CPU0:router(config-ospf)# router-id

192.168.4.3

Configures a router ID for the OSPF process.

Note We recommend using a stable IPv4 address as the

router ID.

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Step 4 redistribute

protocol

[

process-id

] {level-1 |

level-1-2 | level-2} [metric

metric-value

]

[metric-type

type-value

] [match {internal |

external [1 | 2} | nssa-external [1 | 2}] [tag

tag-value

] [route-map

map-tag

| policy

policy-tag

]

Example:

RP/0/RP0/CPU0:router(config-ospf)# redistribute

bgp 1 level-1

RP/0/RP0/CPU0:router(config-router)#

redistribute bgp 1 level-1-2 metric-type 1

Redistributes OSPF routes from one routing domain to

another routing domain.

Redistributes OSPFv3 routes from one routing domain to

another routing domain.

•This command causes the router to become an ASBR

by definition.

•OSPF tags all routes learned through redistribution as

external.

•The protocol and its process ID, if it has one, indicate

the protocol being redistributed into OSPF.

•The metric is the cost you assign to the external route.

The default is 20 for all protocols except BGP, whose

default metric is 1.

•The OSPF example redistributes BGP autonomous

system 1, Level 1 routes into OSPF as Type 2 external

routes.

•The OSPFv3 example redistributes BGP autonomous

system 1, Level 1 and 2 routes into OSPF. The external

link type associated with the default route advertised

into the OSPFv3 routing domain is the Type 1 external

route.

Note RPL is not supported for OSPFv3.

Command or Action Purpose

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Step 5 summary-prefix

address mask

[not-advertise]

[tag

tag

]

summary-prefix

ipv6-prefix

prefix-length

[not-advertise] [tag

tag

]

Example:

RP/0/RP0/CPU0:router(config-ospf)#

summary-prefix 10.1.0.0 255.255.0.0

RP/0/RP0/CPU0:router(config-router)#

summary-prefix 2010:11:22::/32

(Optional) Creates aggregate addresses for OSPF.

(Optional) Creates aggregate addresses for OSPFv3.

•This command provides external route summarization

of the non-OSPF routes.

•External ranges that are being summarized should be

contiguous. Summarization of overlapping ranges from

two different routers could cause packets to be sent to

the wrong destination.

•This command is optional. If you do not specify it, each

route is included in the link-state database and

advertised in LSAs.

•In the OSPFv2 example, the summary address 10.1.0.0

includes address 10.1.1.0, 10.1.2.0, 10.1.3.0, and so on.

Only the address 10.1.0.0 is advertised in an external

LSA.

•In the OSPFv3 example, the summary address

2010:11:22::/32 has addresses such as

2010:11:22:0:1000::1, 2010:11:22:0:2000:679:1, and

so on. Only the address 2010:11:22::/32 is advertised in

the external LSA.

Step 6 end

commit

Example:

RP/0/RP0/CPU0:router(config-ospf)# end

RP/0/RP0/CPU0:router(config-ospf)# commit

Saves configuration changes.

•When you issue the end command, the system prompts

you to commit changes:

Uncommitted changes found, commit them before

exiting(yes/no/cancel)?

[cancel]:

–

Entering yes saves configuration changes to the

running configuration file, exits the configuration

session, and returns the router to EXEC mode.

–

Entering no exits the configuration session and

returns the router to EXEC mode without

committing the configuration changes.

–

Entering cancel leaves the router in the current

configuration session without exiting or

committing the configuration changes.

•Use the commit command to save the configuration

changes to the running configuration file and remain

within the configuration session.

Command or Action Purpose

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Cisco IOS XR Routing Configuration Guide

Configuring OSPF Shortest Path First Throttling

This task explains how to configure SPF scheduling in millisecond intervals and potentially delay SPF

calculations during times of network instability. This task is optional.

Prerequisites

See the “OSPF Shortest Path First Throttling” section on page RC-139 for information about OSPF SPF

throttling.

SUMMARY STEPS

1. configure

2. router ospf process-name

router ospfv3 process-name

3. router-id {ipv4-address | interface-type interface-instance}

4. timers throttle spf spf-start spf-hold spf-max-wait

5. area area-id

6. interface type instance

7. end

commit

8. show ospf [process-name]

show ospfv3 [process-name]

DETAILED STEPS

Command or Action Purpose

Step 1 configure

Example:

RP/0/RP0/CPU0:router# configure

Enters global configuration mode.

Step 2 router ospf

process-name

router ospfv3

process-name

Example:

RP/0/RP0/CPU0:router(config)# router ospf 1

RP/0/RP0/CPU0:router(config)# router ospfv3 1

Enables OSPF routing for the specified routing process, and

places the router in router configuration mode.

Enables OSPFv3 routing for the specified routing process,

and places the router in router ospfv3 configuration mode.

Note The process-name argument is any alphanumeric

string no longer than 40 characters.

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Step 3 router-id {

ipv4-address

interface-type

interface-instance

}

Example:

RP/0/RP0/CPU0:router(config-ospf)# router-id

192.168.4.3

Configures a router ID for the OSPF process.

Note We recommend using a stable IPv4 address as the

router ID.

Step 4 timers throttle spf

spf-start spf-hold

spf-max-wait

Example:

RP/0/RP0/CPU0:router(config-ospf)# timers

throttle spf 10 4800 90000

Sets SPF throttling timers.

Step 5 area

area-id

Example:

RP/0/RP0/CPU0:router(config-ospf)# area 0

Enters area configuration mode and configures a backbone

area.

•The area-id argument can be entered in dotted-decimal

or IPv4 address notation, such as area 1000 or

area 0.0.3.232. However, you must choose one form or

the other for an area. We recommend using the IPv4

address notation.

Step 6 interface

type instance

Example:

RP/0/RP0/CPU0:router(config-ospf-ar)# interface

POS 0/1/0/3

Enters interface configuration mode and associates one or

more interfaces to the area.

Command or Action Purpose

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Examples

In the following example, the show ospf EXEC command is used to verify that the initial SPF schedule

delay time, minimum hold time, and maximum wait time are configured correctly. Additional details are

displayed about the OSPF process, such as the router type and redistribution of routes.

RP/0/RP0/CPU0:router# show ospf 1

Routing Process "ospf 1" with ID 192.168.4.3

Supports only single TOS(TOS0) routes

Supports opaque LSA

It is an autonomous system boundary router

Redistributing External Routes from,

ospf 2

Initial SPF schedule delay 5 msecs

Minimum hold time between two consecutive SPFs 100 msecs

Maximum wait time between two consecutive SPFs 1000 msecs

Minimum LSA interval 5 secs. Minimum LSA arrival 1 secs

Number of external LSA 0. Checksum Sum 00000000

Number of opaque AS LSA 0. Checksum Sum 00000000

Number of DCbitless external and opaque AS LSA 0

Number of DoNotAge external and opaque AS LSA 0

Number of areas in this router is 1. 1 normal 0 stub 0 nssa

External flood list length 0

Step 7 end

commit

Example:

RP/0/RP0/CPU0:router(config-ospf-ar-if)# end

RP/0/RP0/CPU0:router(config-ospf-ar-if)# commit

Saves configuration changes.

•When you issue the end command, the system prompts

you to commit changes:

Uncommitted changes found, commit them before

exiting(yes/no/cancel)?

[cancel]:

–

Entering yes saves configuration changes to the

running configuration file, exits the configuration

session, and returns the router to EXEC mode.

–

Entering no exits the configuration session and

returns the router to EXEC mode without

committing the configuration changes.

–

Entering cancel leaves the router in the current

configuration session without exiting or

committing the configuration changes.

•Use the commit command to save the configuration

changes to the running configuration file and remain

within the configuration session.

Step 8 show ospf [

process-name

]

show ospfv3 [

process-name

]

Example:

RP/0/RP0/CPU0:router# show ospf 1

RP/0/RP0/CPU0:router# show ospfv3 2

(Optional) Displays SPF throttling timers.

Command or Action Purpose

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Cisco IOS XR Routing Configuration Guide

Non-Stop Forwarding enabled

Note For a description of each output display field, see the show ospf command in the OSPF Commands on

Cisco IOS XR Software module in the Cisco IOS XR Routing Command Reference document.

Configuring Nonstop Forwarding for OSPF Version 2

This task explains how to configure OSPF NSF on your NSF-capable router. This task is optional.

Prerequisites

OSPF NSF requires that all neighbor networking devices be NSF aware, which happens automatically

after you install the Cisco IOS XR image on the router. If an NSF-capable router discovers that it has

non-NSF-aware neighbors on a particular network segment, it disables NSF capabilities for that

segment. Other network segments composed entirely of NSF-capable or NSF-aware routers continue to

provide NSF capabilities.

See the “Nonstop Forwarding for OSPF Version 2” section on page RC-140 for conceptual information.

Restrictions

The following are restrictions when configuring nonstop forwarding:

•OSPF Cisco NSF for virtual links is not supported.

•Neighbors must be NSF aware.

SUMMARY STEPS

1. configure

2. router ospf process-name

3. router-id {ipv4-address | interface-type interface-instance}

4. nsf

nsf enforce global

5. nsf interval seconds

6. end

commit

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DETAILED STEPS

Command or Action Purpose

Step 1 configure

Example:

RP/0/RP0/CPU0:router# configure

Enters global configuration mode.

Step 2 router ospf

process-name

Example:

RP/0/RP0/CPU0:router(config)# router ospf 1

Enables OSPF routing for the specified routing process, and

places the router in router configuration mode.

Note The process-name argument is any alphanumeric

string no longer than 40 characters.

Step 3 router-id {

ipv4-address

interface-type

interface-instance

}

Example:

RP/0/RP0/CPU0:router(config-ospf)# router-id

192.168.4.3

Configures a router ID for the OSPF process.

Note We recommend using a stable IPv4 address as the

router ID.

Step 4 nsf

nsf enforce global

Example:

RP/0/RP0/CPU0:router(config-ospf)# nsf

RP/0/RP0/CPU0:router(config-ospf)# nsf enforce

global

Enables OSPF NSF operations.

•Use the nsf command without the optional enforce and

global keywords to abort the NSF restart mechanism on

the interfaces of detected non-NSF neighbors and allow

NSF neighbors to function properly.

•Use the nsf command with the optional enforce and

global keywords if the router is expected to perform

NSF during restart. However, if non-NSF neighbors are

detected, NSF restart is canceled for the entire OSPF

process.

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Configuring OSPF Version 2 for MPLS Traffic Engineering

This task explains how to configure OSPF for MPLS TE. This task is optional.

For a description of the MPLS TE tasks and commands that allow you to configure the router to support

tunnels, configure an MPLS tunnel that OSPF can use, and troubleshoot MPLS TE, see the Implementing

MPLS Traffic Engineering Configuration Guide.

Prerequisites

Your network must support the following Cisco IOS XR features before you enable MPLS TE for OSPF

on your router:

•MPLS

•IP Cisco Express Forwarding (CEF)

Note You must enter the commands in the following task on every OSPF router in the traffic-engineered

portion of your network.

Step 5 nsf interval

seconds

Example:

RP/0/RP0/CPU0:router(config-ospf)# nsf interval

120

Sets the minimum time between NSF restart attempts.

Note When you use this command, the OSPF process

must be up for at least 90 seconds before OSPF

attempts to perform an NSF restart.

Step 6 end

commit

Example:

RP/0/RP0/CPU0:router(config-ospf)# end

RP/0/RP0/CPU0:router(config-ospf)# commit

Saves configuration changes.

•When you issue the end command, the system prompts

you to commit changes:

Uncommitted changes found, commit them before

exiting(yes/no/cancel)?

[cancel]:

–

Entering yes saves configuration changes to the

running configuration file, exits the configuration

session, and returns the router to EXEC mode.

–

Entering no exits the configuration session and

returns the router to EXEC mode without

committing the configuration changes.

–

Entering cancel leaves the router in the current

configuration session without exiting or

committing the configuration changes.

•Use the commit command to save the configuration

changes to the running configuration file and remain

within the configuration session.

Command or Action Purpose

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Restrictions

MPLS traffic engineering currently supports only a single OSPF area.

SUMMARY STEPS

1. configure

2. router ospf process-name

3. router-id {ipv4-address | interface-type interface-instance}

4. mpls traffic-eng area area-id

5. mpls traffic-eng router-id {ip-address | interface-type interface-instance}

6. area area-id

7. interface type instance

8. end

commit

9. show ospf [process-name] [area-id] mpls traffic-eng {link | fragment}

DETAILED STEPS

Command or Action Purpose

Step 1 configure

Example:

RP/0/RP0/CPU0:router# configure

Enters global configuration mode.

Step 2 router ospf

process-name

Example:

RP/0/RP0/CPU0:router(config)# router ospf 1

Enables OSPF routing for the specified routing process, and

places the router in router configuration mode.

Note The process-name argument is any alphanumeric

string no longer than 40 characters.

Step 3 router-id {

ipv4-address

interface-type

interface-instance

}

Example:

RP/0/RP0/CPU0:router(config-ospf)# router-id

192.168.4.3

Configures a router ID for the OSPF process.

Note We recommend using a stable IPv4 address as the

router ID.

Step 4 mpls traffic-eng area

area-id

Example:

RP/0/RP0/CPU0:router(config-ospf)# mpls

traffic-eng area 0

Configures the OSPF area for MPLS TE.

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Step 5 mpls traffic-eng router-id {

ip-address

interface-type interface-instance

}

Example:

RP/0/RP0/CPU0:router(config-ospf)# mpls

traffic-eng router-id loopback 0

(Optional) Specifies that the traffic engineering router

identifier for the node is the IP address associated with a

given interface.

•This IP address is flooded to all nodes in TE LSAs.

•For all traffic engineering tunnels originating at other

nodes and ending at this node, you must set the tunnel

destination to the traffic engineering router identifier of

the destination node because that is the address that the

traffic engineering topology database at the tunnel head

uses for its path calculation.

•We recommend that loopback interfaces be used for

MPLS TE router ID because they are more stable than

physical interfaces.

Step 6 area

area-id

Example:

RP/0/RP0/CPU0:router(config-ospf)# area 0

Enters area configuration mode and configures an area for

the OSPF process.

•The area-id argument can be entered in dotted-decimal

or IPv4 address notation, such as area 1000 or

area 0.0.3.232. However, you must choose one form or

the other for an area.

Step 7 interface

type instance

Example:

RP/0/RP0/CPU0:router(config-ospf-ar)# interface

interface loopback0

Enters interface configuration mode and associates one or

more interfaces to the area.

Command or Action Purpose

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Examples

This section provides the following output examples:

•Sample Output for the show ospf Command Before Configuring MPLS TE, page RC-178

•Sample Output for the show ospf mpls traffic-eng Command, page RC-179

•Sample Output for the show ospf Command After Configuring MPLS TE, page RC-180

Sample Output for the show ospf Command Before Configuring MPLS TE

In the following example, the show route ospf EXEC command verifies that POS interface 0/3/0/0 exists

and MPLS TE is not configured:

RP/0/RP0/CPU0:router# show route ospf 1 0

O E2 192.168.10.0/24 [110/20] via 192.168.1.2, 00:02:50, POS 0/3/0/0

[110/20] via 192.168.4.1, 00:02:50, POS 0/3/0/1

O E2 192.168.11.0/24 [110/20] via 192.168.1.2, 00:02:50, POS 0/3/0/0

[110/20] via 192.168.4.1, 00:02:50, POS 0/3/0/1

O E2 192.168.244.0/24 [110/20] via 192.168.1.2, 00:02:50, POS 0/3/0/0

[110/20] via 192.168.4.1, 00:02:50, POS 0/3/0/1

O 192.168.12.0/24 [110/2] via 192.168.1.2, 00:02:50, POS 0/3/0/0

[110/2] via 192.168.4.1, 00:02:50, POS 0/3/0/1

Step 8 end

commit

Example:

RP/0/RP0/CPU0:router(config-ospf-ar-if)# end

RP/0/RP0/CPU0:router(config-ospf-ar-if)# commit

Saves configuration changes.

•When you issue the end command, the system prompts

you to commit changes:

Uncommitted changes found, commit them before

exiting(yes/no/cancel)?

[cancel]:

–

Entering yes saves configuration changes to the

running configuration file, exits the configuration

session, and returns the router to EXEC mode.

–

Entering no exits the configuration session and

returns the router to EXEC mode without

committing the configuration changes.

–

Entering cancel leaves the router in the current

configuration session without exiting or

committing the configuration changes.

•Use the commit command to save the configuration

changes to the running configuration file and remain

within the configuration session.

Step 9 show ospf [

process-name

] [

area-id

] mpls

traffic-eng {link | fragment}

Example:

RP/0/RP0/CPU0:router# show ospf 1 0 mpls

traffic-eng link

(Optional) Displays information about the links and

fragments available on the local router for MPLS TE.

Command or Action Purpose

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Cisco IOS XR Routing Configuration Guide

Sample Output for the show ospf mpls traffic-eng Command

In the following example, the show ospf mpls traffic-eng EXEC command verifies that the MPLS TE

fragments are configured correctly:

RP/0/RP0/CPU0:router# show ospf 1 mpls traffic-eng fragment

OSPF Router with ID (192.168.4.3) (Process ID 1)

Area 0 has 1 MPLS TE fragment. Area instance is 3.

MPLS router address is 192.168.4.2

Next fragment ID is 1

Fragment 0 has 1 link. Fragment instance is 3.

Fragment has 0 link the same as last update.

Fragment advertise MPLS router address

Link is associated with fragment 0. Link instance is 3

Link connected to Point-to-Point network

Link ID :55.55.55.55

Interface Address :192.168.50.21

Neighbor Address :192.168.4.1

Admin Metric :0

Maximum bandwidth :19440000

Maximum global pool reservable bandwidth :25000000

Maximum sub pool reservable bandwidth :3125000

Number of Priority :8

Global pool unreserved BW

Priority 0 : 25000000 Priority 1 : 25000000

Priority 2 : 25000000 Priority 3 : 25000000

Priority 4 : 25000000 Priority 5 : 25000000

Priority 6 : 25000000 Priority 7 : 25000000

Sub pool unreserved BW

Priority 0 : 3125000 Priority 1 : 3125000

Priority 2 : 3125000 Priority 3 : 3125000

Priority 4 : 3125000 Priority 5 : 3125000

Priority 6 : 3125000 Priority 7 : 3125000

Affinity Bit :0

In the following example, the show ospf mpls traffic-eng EXEC command verifies that the MPLS TE

links on area instance 3 are configured correctly:

RP/0/RP0/CPU0:router# show ospf mpls traffic-eng link

OSPF Router with ID (192.168.4.1) (Process ID 1)

Area 0 has 1 MPLS TE links. Area instance is 3.

Links in hash bucket 53.

Link is associated with fragment 0. Link instance is 3

Link connected to Point-to-Point network

Link ID :192.168.50.20

Interface Address :192.168.20.50

Neighbor Address :192.168.4.1

Admin Metric :0

Maximum bandwidth :19440000

Maximum global pool reservable bandwidth :25000000

Maximum sub pool reservable bandwidth :3125000

Number of Priority :8

Global pool unreserved BW

Priority 0 : 25000000 Priority 1 : 25000000

Priority 2 : 25000000 Priority 3 : 25000000

Priority 4 : 25000000 Priority 5 : 25000000

Priority 6 : 25000000 Priority 7 : 25000000

Sub pool unreserved BW

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Priority 0 : 3125000 Priority 1 : 3125000

Priority 2 : 3125000 Priority 3 : 3125000

Priority 4 : 3125000 Priority 5 : 3125000

Priority 6 : 3125000 Priority 7 : 3125000

Affinity Bit :0

Sample Output for the show ospf Command After Configuring MPLS TE

In the following example, the show route ospf EXEC command verifies that the MPLS TE tunnels

replaced POS interface 0/3/0/0 and that configuration was performed correctly:

RP/0/RP0/CPU0:router# show route ospf 1 0

O E2 192.168.10.0/24 [110/20] via 0.0.0.0, 00:00:15, tunnel2

O E2 192.168.11.0/24 [110/20] via 0.0.0.0, 00:00:15, tunnel2

O E2 192.168.1244.0/24 [110/20] via 0.0.0.0, 00:00:15, tunnel2

O 192.168.12.0/24 [110/2] via 0.0.0.0, 00:00:15, tunnel2

Verifying OSPF Configuration and Operation

This task explains how to verify the configuration and operation of OSPF.

Note To execute OSPFv3 commands for this task, replace ospf with ospfv3 in Steps 1 through 7.

SUMMARY STEPS

1. show ospf [process-name]

2. show ospf [process-name] border-routers [router-id]

3. show ospf [process-name] database

4. show ospf [process-name] [area-id] flood-list interface type instance

5. show ospf [process-name] [area-id] neighbor [interface-type interface-instance] [neighbor-id]

[detail]

6. clear ospf [process-name] process

7. clear ospf [process-name] statistics [neighbor [interface-type interface-instance] [ip-address]]

DETAILED STEPS

Command or Action Purpose

Step 1 show ospf [

process-name

]

Example:

RP/0/RP0/CPU0:router# show ospf group1

(Optional) Displays general information about OSPF

routing processes.

Step 2 show ospf [

process-name

] border-routers

[

router-id

]

Example:

RP/0/RP0/CPU0:router# show ospf group1

border-routers

(Optional) Displays the internal OSPF routing table entries

to an ABR and ASBR.

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Configuring OSPFv3 Graceful Restart

This section describes the following tasks for configuring a graceful restart of an OSPFv3 process:

•Enabling Graceful Restart, page RC-182

•Configuring the Maximum Lifetime of a Graceful Restart, page RC-182

•Configuring the Minimum Time Required Between Restarts, page RC-183

•Configuring the Helper Level of the Router, page RC-184

•Displaying Information About Graceful Restart, page RC-185

Step 3 show ospf [

process-name

] database

Example:

RP/0/RP0/CPU0:router# show ospf group2 database

(Optional) Displays the lists of information related to the

OSPF database for a specific router.

•The various forms of this command deliver information

about different OSPF LSAs.

Step 4 show ospf [

process-name

] [

area-id

] flood-list

interface

type instance

Example:

RP/0/RP0/CPU0:router# show ospf 100 flood-list

interface pos 0/3/0/0

(Optional) Displays a list of OSPF LSAs waiting to be

flooded over an interface.

Step 5 show ospf [

process-name

] [

area-id

] neighbor

[

interface-type interface-instance

]

[

neighbor-id

] [detail]

Example:

RP/0/RP0/CPU0:router# show ospf 100 neighbor

(Optional) Displays OSPF neighbor information on an

individual interface basis.

Step 6 clear ospf [

process-name

] process

Example:

RP/0/RP0/CPU0:router# clear ospf 100 process

(Optional) Resets an OSPF router process without stopping

and restarting it.

Step 7 clear ospf [

process-name

] statistics [neighbor

[

interface-type interface-instance

]

[

ip-address

]]

Example:

RP/0/RP0/CPU0:router# clear ospf 100 statistics

(Optional) Clears the OSPF statistics of neighbor state

transitions.

Command or Action Purpose

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Enabling Graceful Restart

This section describes how to enable an OSPFv3 graceful restart on the current router. By default, this

feature is disabled.

SUMMARY STEPS

1. configuration

2. router ospfv3

3. graceful-restart

DETAILED STEPS

Configuring the Maximum Lifetime of a Graceful Restart

This section describes the task of modifying the total time that a router can be in graceful restart mode.

The default lifetime is 95 seconds. The range is 90–3600 seconds.

SUMMARY STEPS

1. configuration

2. router ospfv3

3. graceful-restart lifetime

Command or Action Purpose

Step 1 config

Example:

RP/0/RP0/CPU0:single10-hfr#config

RP/0/RP0/CPU0:single10-hfr(config)

Enters global configuration mode.

Step 2 router ospfv3

process-name

Example:

RP/0/RP0/CPU0:single10-hfr(config)# router

ospfv3 test

Enters router configuration mode for OSPFv3. The process

name is a WORD that uniquely identifies an OSPF routing

process. The process name is any alphanumeric string no

longer than 40 characters without spaces.

Step 3 graceful-restart

Example:

RP/0/RP0/CPU0:single10-hfr(config-ospfv3)#grace

ful-restart

Enable graceful restart on the current router.

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DETAILED STEPS

Configuring the Minimum Time Required Between Restarts

This section describes the task of modifying the minimal time that is required between allowable

graceful restarts. The purpose of this interval is to prevent the waste of system resources if the OSPFv3

process is repeatedly crashing for reasons that must be diagnosed. The default value for the interval is

90 seconds. The range is 90–3600 seconds.

SUMMARY STEPS

1. configuration

2. router ospfv3

3. graceful-restart interval

Command or Action Purpose

Step 1 config

Example:

RP/0/RP0/CPU0:single10-hfr#config

RP/0/RP0/CPU0:single10-hfr(config)

Enters global configuration mode.

Step 2 router ospfv3 <

process-name>

Example:

RP/0/RP0/CPU0:single10-hfr(config)# router

ospfv3 test

Enters router configuration mode for OSPFv3. The process

name is a WORD that uniquely identifies an OSPF routing

process. The process name is any alphanumeric string no

longer than 40 characters without spaces.

Step 3 graceful-restart lifetime

Example:

RP/0/RP0/CPU0:single10-hfr(config-ospfv3)#grace

ful-restart lifetime 120

Specifies a maximum duration for a graceful restart.

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DETAILED STEPS

Configuring the Helper Level of the Router

This section describes the task of disabling the helper mode on the current router. By default, a router

that is capable of doing an OSPFv3 graceful restart is also enabled to be a helper to a node in graceful

mode. The graceful-restart helper command lets you disable the current router’s helper capability.

SUMMARY STEPS

1. configuration

2. router ospfv3

3. graceful-restart helper [disable]

Command or Action Purpose

Step 1 config

Example:

RP/0/RP0/CPU0:single10-hfr#config

RP/0/RP0/CPU0:single10-hfr(config)

Enters global configuration mode.

Step 2 router ospfv3 <

process-name>

Example:

RP/0/RP0/CPU0:single10-hfr(config)# router

ospfv3 test

Enters router configuration mode for OSPFv3. The process

name is a WORD that uniquely identifies an OSPF routing

process. The process name is any alphanumeric string no

longer than 40 characters without spaces.

Step 3 graceful-restart interval <

seconds

Example:

RP/0/RP0/CPU0:single10-hfr(config-ospfv3)#grace

ful-restart interval 120

Specifies the interval (minimal time) between graceful

restarts on the current router.

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DETAILED STEPS

Displaying Information About Graceful Restart

This section describes the tasks you can use to display information about a graceful restart.

•To see if the feature is enabled and when the last graceful restart ran, use the show ospf command.

To see details for an OSPFv3 instance, use the show ospf process-name database grace command.

Displaying the State of the Graceful Restart Feature

The following screen output shows the state of the graceful restart capability on the local router:

RP/0/0/CPU0:LA#show ospfv3 test database grace

Routing Process “ospfv3 test” with ID 2.2.2.2

Initial SPF schedule delay 5000 msecs

Minimum hold time between two consecutive SPFs 10000 msecs

Maximum wait time between two consecutive SPFs 10000 msecs

Initial LSA throttle delay 0 msecs

Minimum hold time for LSA throttle 5000 msecs

Maximum wait time for LSA throttle 5000 msecs

Minimum LSA arrival 1000 msecs

LSA group pacing timer 240 secs

Interface flood pacing timer 33 msecs

Retransmission pacing timer 66 msecs

Maximum number of configured interfaces 255

Number of external LSA 0. Checksum Sum 00000000

Number of areas in this router is 1. 1 normal 0 stub 0 nssa

Graceful Restart enabled, last GR 11:12:26 ago (took 6 secs)

Area BACKBONE(0)

Number of interfaces in this area is 1

SPF algorithm executed 1 times

Number of LSA 6. Checksum Sum 0x0268a7

Number of DCbitless LSA 0

Number of indication LSA 0

Number of DoNotAge LSA 0

Flood list length 0

RP/0/0/CPU0:LA#

Command or Action Purpose

Step 1 config

Example:

RP/0/RP0/CPU0:single10-hfr#config

RP/0/RP0/CPU0:single10-hfr(config)

Enters global configuration mode.

Step 2 router ospfv3 <

process-name>

Example:

RP/0/RP0/CPU0:single10-hfr(config)# router

ospfv3 test

Enters router configuration mode for OSPFv3. The process

name is a WORD that uniquely identifies an OSPF routing

process. The process name is any alphanumeric string no

longer than 40 characters without spaces.

Step 3 graceful-restart helper

Example:

RP/0/RP0/CPU0:single10-hfr(config-ospfv3)#grace

ful-restart helper disable

Disables the helper capability.

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Displaying Graceful Restart Information for an OSPFv3 Instance

The following screen output shows the link state for the instance of OSPFv3 called test:

RP/0/0/CPU0:LA#show ospfv3 test database grace

OSPFv3 Router with ID (2.2.2.2) (Process ID test)

Router Link States (Area 0)

ADV Router Age Seq# Fragment ID Link count Bits

1.1.1.1 1949 0x8000000e 0 1 None

2.2.2.2 2007 0x80000011 0 1 None

Link (Type-8) Link States (Area 0)

ADV Router Age Seq# Link ID Interface

1.1.1.1 180 0x80000006 1 PO0/2/0/0

s2.2.2.2 2007 0x80000006 1 PO0/2/0/0

Intra Area Prefix Link States (Area 0)

ADV Router Age Seq# Link ID Ref-lstype Ref-LSID

1.1.1.1 180 0x80000006 0 0x2001 0

2.2.2.2 2007 0x80000006 0 0x2001 0

Grace (Type-11) Link States (Area 0)

ADV Router Age Seq# Link ID Interface

2.2.2.2 2007 0x80000005 1 PO0/2/0/0

RP/0/0/CPU0:LA#

Enabling Multicast-Intact for OSPFv2

This optional task describes how to enable multicast-intact for OSPFv2 routes that use IPv4 addresses.

Summary Steps

1. configure

2. router ospf instance-id

3. mpls traffic-eng multicast-intact

4. end

commit

DETAILED STEPS

Command or Action Purpose

Step 1 configure

Example:

RP/0/RP0/CPU0:router# configure

Enters global configuration mode.

Step 2 router ospf

instance-id

Example:

RP/0/RP0/CPU0:router(config)# router ospf isp

Enables OSPF routing for the specified routing process, and

places the router in router configuration mode. In this

example, the OSPF instance is called isp.

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Configuration Examples for Implementing OSPF on Cisco IOS XR Software

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Cisco IOS XR Routing Configuration Guide

Configuration Examples for Implementing OSPF on Cisco IOS XR

Software

This section provides the following configuration examples:

•Cisco IOS XR for OSPF Version 2 Configuration: Example, page RC-188

•CLI Inheritance and Precedence for OSPF Version 2: Example, page RC-189

•MPLS TE for OSPF Version 2: Example, page RC-190

•ABR with Summarization for OSPFv3: Example, page RC-190

•ABR Stub Area for OSPFv3: Example, page RC-190

•ABR Totally Stub Area for OSPFv3: Example, page RC-191

•Route Redistribution for OSPFv3: Example, page RC-191

•Virtual Link Configured Through Area 1 for OSPFv3: Example, page RC-191

Step 3 mpls traffic-eng multicast-intact

Example:

RP/0/RP0/CPU0:router(config-isis)# mpls

traffic-eng multicast-intact

Enables multicast-intact.

Step 4 end

commit

Example:

RP/0/RP0/CPU0:router(config-isis-af)# end

RP/0/RP0/CPU0:router(config-isis-af)# commit

Saves configuration changes.

•When you issue the end command, the system prompts

you to commit changes:

Uncommitted changes found, commit them before

exiting(yes/no/cancel)?

[cancel]:

–

Entering yes saves configuration changes to the

running configuration file, exits the configuration

session, and returns the router to EXEC mode.

–

Entering no exits the configuration session and

returns the router to EXEC mode without

committing the configuration changes.

–

Entering cancel leaves the router in the current

configuration session without exiting or

committing the configuration changes.

•Use the commit command to save the configuration

changes to the running configuration file and remain

within the configuration session.

Command or Action Purpose

Implementing OSPF on Cisco IOS XR Software

Configuration Examples for Implementing OSPF on Cisco IOS XR Software

RC-188

Cisco IOS XR Routing Configuration Guide

Cisco IOS XR for OSPF Version 2 Configuration: Example

The following example shows how an OSPF interface is configured for an area in

Cisco IOS XR software.

In Cisco IOS XR software, area 0 must be explicitly configured with the area command and all

interfaces that are in the range from 10.1.2.0 to 10.1.2.255 are bound to area 0. Interfaces are configured

with the interface command (while the router is in area configuration mode) and the area keyword is

not included in the interface statement.

Cisco IOS XR Software Configuration

interface POS 0/3/0/0

ip address 10.1.2.1 255.255.255.255

negotiation auto

router ospf 1

router-id 10.2.3.4

area 0

interface POS 0/3/0/0

The following example shows how OSPF interface parameters are configured for an area in

Cisco IOS XR software.

In Cisco IOS XR software, OSPF interface-specific parameters are configured in interface configuration

mode and explicitly defined for area 0. In addition, the ip ospf keywords are no longer required.

Cisco IOS XR Software Configuration

interface POS 0/3/0/0

ip address 10.1.2.1 255.255.255.0

negotiation auto

router ospf 1

router-id 10.2.3.4

area 0

interface POS 0/3/0/0

cost 77

mtu-ignore

authentication message-digest

message-digest-key 1 md5 0 test

The following example shows the hierarchical CLI structure of Cisco IOS XR software.

In Cisco IOS XR software, OSPF areas must be explicitly configured, and interfaces configured under

the area configuration mode are explicitly bound to that area. In this example, interface 10.1.2.0/24 is

bound to area 0 and interface 10.1.3.0/24 is bound to area 1.

Cisco IOS XR Software Configuration

interface POS 0/3/0/0

ip address 10.1.2.1 255.255.255.0

negotiation auto

interface POS 0/3/0/1

ip address 10.1.3.1 255.255.255.0

negotiation auto

Implementing OSPF on Cisco IOS XR Software

Configuration Examples for Implementing OSPF on Cisco IOS XR Software

RC-189

Cisco IOS XR Routing Configuration Guide

router ospf 1

router-id 10.2.3.4

area 0

interface POS 0/3/0/0

area 1

interface POS 0/3/0/1

CLI Inheritance and Precedence for OSPF Version 2: Example

The following example configures the cost parameter at different hierarchical levels of the OSPF

topology, and illustrates how the parameter is inherited and how only one setting takes precedence.

According to the precedence rule, the most explicit configuration is used.

The cost parameter is set to 5 in router configuration mode for the OSPF process. Area 1 sets the cost to

15 and area 6 sets the cost to 30. All interfaces in area 0 inherit a cost of 5 from the OSPF process because

the cost was not set in area 0 or its interfaces.

In area 1, every interface has a cost of 15 because the cost is set in area 1 and 15 overrides the value 5

that was set in router configuration mode.

Area 4 does not set the cost, but POS interface 01/0/2 sets the cost to 20. The remaining interfaces in

area 4 have a cost of 5 that is inherited from the OSPF process.

Area 6 sets the cost to 30, which is inherited by POS interfaces 0/1/0/3 and 0/2/0/3. POS interface 0/3/0/3

uses the cost of 1, which is set in interface configuration mode.

router ospf 1

router-id 10.5.4.3

cost 5

area 0

interface POS 0/1/0/0

interface POS 0/2/0/0

interface POS 0/3/0/0

area 1

cost 15

interface POS 0/1/0/1

interface POS 0/2/0/1

interface POS 0/3/0/1

area 4

interface POS 0/1/0/2

cost 20

interface POS 0/2/0/2

interface POS 0/3/0/2

area 6

cost 30

interface POS 0/1/0/3

Implementing OSPF on Cisco IOS XR Software

Configuration Examples for Implementing OSPF on Cisco IOS XR Software

RC-190

Cisco IOS XR Routing Configuration Guide

interface POS 0/2/0/3

interface POS 0/3/0/3

cost 1

MPLS TE for OSPF Version 2: Example

The following example shows how to configure the OSPF portion of MPLS TE. However, you still need

to build an MPLS TE topology and create an MPLS TE tunnel. See the Cisco IOS XR MPLS

Configuration Guide for information.

In this example, loopback interface 0 is associated with area 0 and area 0 is declared to be an MPLS area:

interface Loopback 0

ip address 10.10.10.10 255.255.255.0

interface POS 0/2/0/0

ip address 10.1.2.2 255.255.255.0

router ospf 1

router-id 10.10.10.10

nsf

auto-cost reference-bandwidth 10000

area 0

interface POS 0/2/0/0

interface Loopback 0

mpls traffic-eng area 0

mpls traffic-eng router-id Loopback 0

ABR with Summarization for OSPFv3: Example

The following example shows the prefix range 2300::/16 summarized from area 1 into the backbone:

router ospfv3 1

router-id 192.168.0.217

area 0

interface POS 0/2/0/1

area 1

range 2300::/16

interface POS 0/2/0/0

ABR Stub Area for OSPFv3: Example

The following example shows that area 1 is configured as a stub area:

router ospfv3 1

router-id 10.0.0.217

area 0

interface POS 0/2/0/1

area 1

stub

interface POS 0/2/0/0

Implementing OSPF on Cisco IOS XR Software

Configuration Examples for Implementing OSPF on Cisco IOS XR Software

RC-191

Cisco IOS XR Routing Configuration Guide

ABR Totally Stub Area for OSPFv3: Example

The following example shows that area 1 is configured as a totally stub area:

router ospfv3 1

router-id 10.0.0.217

area 0

interface POS 0/2/0/1

area 1

stub no-summary

interface POS 0/2/0/0

Route Redistribution for OSPFv3: Example

The following example uses prefix lists to limit the routes redistributed from other protocols.

Only routes with 9898:1000 in the upper 32 bits and with prefix lengths from 32 to 64 are redistributed

from BGP 42. Only routes not matching this pattern are redistributed from BGP 1956.

ipv6 prefix-list list1

seq 10 permit 9898:1000::/32 ge 32 le 64

ipv6 prefix-list list2

seq 10 deny 9898:1000::/32 ge 32 le 64

seq 20 permit ::/0 le 128

router ospfv3 1

router-id 10.0.0.217

redistribute bgp 42

redistribute bgp 1956

distribute-list prefix-list list1 out bgp 42

distribute-list prefix-list list2 out bgp 1956

area 1

interface POS 0/2/0/0

Virtual Link Configured Through Area 1 for OSPFv3: Example

This example shows how to set up a virtual link to connect the backbone through area 1 for the OSPFv3

topology that consists of areas 0 and 1 and virtual links 10.0.0.217 and 10.0.0.212:

ABR 1 Configuration

router ospfv3 1

router-id 10.0.0.217

area 0

interface POS 0/2/0/1

area 1

virtual-link 10.0.0.212

interface POS 0/2/0/0

ABR 2 Configuration

router ospfv3 1

router-id 10.0.0.212

area 0

interface POS 0/3/0/1

area 1

virtual-link 10.0.0.217

interface POS 0/2/0/0

Implementing OSPF on Cisco IOS XR Software

Where to Go Next

RC-192

Cisco IOS XR Routing Configuration Guide

Virtual Link Configured with MD5 Authentication for OSPF Version 2: Example

The following examples show how to configure a virtual link to your backbone and apply MD5

authentication. You must perform the steps described on both ABRs at each end of the virtual link.

After you explicitly configure the ABRs, the configuration is inherited by all interfaces bound to that

area—unless you override the values and configure them explicitly for the interface.

To understand virtual links, see the “Virtual Link and Transit Area for OSPF” section on page RC-138.

In this example, all interfaces on router ABR1 use MD5 authentication:

router ospf ABR1

router-id 10.10.10.10

authentication message-digest

message-digest-key 100 md5 0 cisco

area 0

interface pos 0/2/0/1

interface pos 0/3/0/0

area 1

interface pos 0/3/0/1

virtual-link 10.10.5.5

In this example, only area 1 interfaces on router ABR3 use MD5 authentication:

router ospf ABR2

router-id 10.10.5.5

area 0

area 1

authentication message-digest

message-digest-key 100 md5 0 cisco

interface pos 0/9/0/1

virtual-link 10.10.10.10

area 3

interface Loopback 0

interface pos 0/9/0/0

Where to Go Next

To configure route maps through the RPL for OSPF Version 2, see the Implementing Routing Policy on

Cisco IOS XR Software document.

To build an MPLS TE topology, create tunnels, and configure forwarding over the tunnel for OSPF

Version 2; see the Cisco IOS XR MPLS Configuration Guide.

Implementing OSPF on Cisco IOS XR Software

Additional References

RC-193

Cisco IOS XR Routing Configuration Guide

Additional References

The following sections provide references related to implementing OSPF on Cisco IOS XR software.

Related Documents

Standards

MIBs

RFCs

Related Topic Document Title

OSPF and OSPFv3 commands: complete command

syntax, command modes, command history, defaults,

usage guidelines, and examples

Cisco IOS XR Routing Command Reference, Release 32

MPLS TE feature information Implementing MPLS Traffic Engineering on Cisco IOS XR Software

module in the Cisco IOS XR MPLS Configuration Guide, Release

3.2

Standards Title

No new or modified standards are supported by this

feature, and support for existing standards has not been

modified by this feature.

—

MIBs MIBs Link

•OSPF-MIB To locate and download MIBs for selected platforms using

Cisco IOS XR software, use the Cisco MIB Locator found at the

following URL:

http://cisco.com/public/sw-center/netmgmt/cmtk/mibs.shtml

RFCs Title

RFC 1587 Not so Stubby Area (NSSA)

RFC 1793 OSPF over demand circuit

RFC 2328 OSPF Version 2

RFC 2740 OSPFv3

RFC 3623 Graceful OSPF Restart (OSPFv2)

Implementing OSPF on Cisco IOS XR Software

Additional References

RC-194

Cisco IOS XR Routing Configuration Guide

Technical Assistance

Description Link

The Cisco Technical Support website contains

thousands of pages of searchable technical content,

including links to products, technologies, solutions,

technical tips, and tools. Registered Cisco.com users

can log in from this page to access even more content.

http://www.cisco.com/techsupport

RC-195

Cisco IOS XR Routing Configuration Guide

Implementing and Monitoring RIB on

Cisco IOS XR Software

Routing Information Base (RIB) is a distributed collection of information about routing connectivity

among all nodes of a network.

Each router maintains a RIB containing the routing information for that router. RIB stores the best routes

from all routing protocols that are running on the system.

This module describes the tasks you need to perform to implement and monitor RIB on your

Cisco IOS XR network.

Note For more information about RIB on the Cisco IOS XR software and complete descriptions of RIB

commands listed in this module, see the “Related Documents” of this module. To locate documentation

for other commands that might appear during the execution of a configuration task, search online in the

Cisco IOS XR software master command index.

Feature History for Implementing and Monitoring RIB on Cisco IOS XR Software

Contents

•Prerequisites for Implementing RIB on Cisco IOS XR Software, page RC-196

•Information About RIB Configuration, page RC-196

•How to Deploy and Monitor RIB, page RC-198

•Configuration Examples for RIB Monitoring, page RC-200

•Where to Go Next, page RC-202

•Additional References, page RC-203

Release Modification

Release 2.0 This feature was introduced on the Cisco CRS-1.

Release 3.0 No modification.

Release 3.2 Support was added for the Cisco XR 12000 Series Router.

Implementing and Monitoring RIB on Cisco IOS XR Software

Prerequisites for Implementing RIB on Cisco IOS XR Software

RC-196

Cisco IOS XR Routing Configuration Guide

Prerequisites for Implementing RIB on Cisco IOS XR Software

•To use this command, you must be in a user group associated with a task group that includes the

proper task IDs. For detailed information about user groups and task IDs, see the Configuring AAA

Services on Cisco IOS XR Software module of the Cisco IOS XR System Security Configuration

Guide.

•RIB is distributed with the base Cisco IOS XR software; as such, it does not have any special

requirements for installation. The following are the requirements for base software installation:

–

Router

–

Cisco IOS XR software

–

Base package

Information About RIB Configuration

To implement the Cisco RIB feature, you must understand the following concepts:

•Overview of RIB, page RC-196

•RIB Data Structures in BGP and Other Protocols, page RC-196

•RIB Administrative Distance, page RC-197

•RIB Support for IPv4 and IPv6, page RC-197

Overview of RIB

Each routing protocol selects its own set of best routes and installs those routes and their attributes in

RIB. RIB stores these routes and selects the best ones from among all routing protocols. Those routes

are downloaded to the line cards for use in forwarding packets. The acronym RIB is used both to refer

to RIB processes and the collection of route data contained within RIB.

Within a protocol, routes are selected based on the metrics in use by that protocol. A protocol downloads

its best routes (lowest or tied metric) to RIB. RIB selects the best overall route by comparing the

administrative distance of the associated protocol.

RIB Data Structures in BGP and Other Protocols

RIB uses processes and maintains data structures distinct from other routing applications, such as Border

Gateway Protocol (BGP) and other unicast routing protocols, or multicast protocols, such as Protocol

Independent Multicast (PIM) or Multicast Source Discovery Protocol (MSDP). However, these routing

protocols use internal data structures similar to what RIB uses, and may internally refer to the data

structures as a RIB. For example, BGP routes are stored in the BGP RIB (BRIB), and multicast routes,

computed by multicast routing protocols such as PIM and MSDP, are stored in the Multicast RIB

(MRIB). RIB processes are not responsible for the BRIB and MRIB, which are handled by BGP and

multicast processes, respectively.

The table used by the line cards and RP to forward packets is called the Forwarding Information Base

(FIB). RIB processes do not build the FIBs. Instead, RIB downloads the set of selected best routes to the

FIB processes, by the Bulk Content Downloader (BCDL) process, onto each line card. FIBs are then

constructed.

Implementing and Monitoring RIB on Cisco IOS XR Software

Information About RIB Configuration

RC-197

Cisco IOS XR Routing Configuration Guide

RIB Administrative Distance

Forwarding is done based on the longest prefix match. If you are forwarding a packet destined to

10.0.2.1, you prefer 10.0.2.0/24 over 10.0.0.0/16 because the mask /24 is longer (and more specific) than

a /16.

Routes from different protocols that have the same prefix and length are chosen based on administrative

distance. For instance, the Open Shortest Path First (OSPF) protocol has an administrative distance of

110, and the Intermediate System-to-Intermediate System (IS-IS) protocol has an administrative

distance of 115. If IS-IS and OSPF both download 10.0.1.0/24 to RIB, RIB would prefer the OSPF route

because OSPF has a lower administrative distance. Administrative distance is used only to choose

between multiple routes of the same length.

The default administrative distances for the common protocols are shown in Table 2.

The administrative distance for some routing protocols (for instance IS-IS, OSPF, and BGP) can be

changed. See the protocol-specific documentation for the proper method to change the administrative

distance of that protocol.

Note Changing the administrative distance of a protocol on some but not all routers can lead to routing loops

and other undesirable behavior. Doing so is not recommended.

RIB Support for IPv4 and IPv6

In Cisco IOS XR software, RIB tables support multicast and unicast routing.

The default routing table for Cisco IOS XR RIB are the unicast and the multicast-unicast RIB tables for

IPv4 and IPv6 routing, respectively. For multicast routing, routing protocols insert unicast routes into

the multicast-unicast RIB table. Multicast protocols then use the information to build multicast routes

(which in turn are stored in the MRIB). See the multicast documentation for more information on using

and configuring multicast.

RIB processes ipv4_rib and ipv6_rib run on the RP card. If process placement functionality is available

and supported by multiple RPs in the router, RIB processes can be placed on any available node.

Table 2 Default Administrative Distances

Protocol Administrative Distance Default

Connected or local routes 0

Static routes 1

External BGP routes 20

OSPF routes 110

IS-IS routes 115

Internal BGP routes 200

Implementing and Monitoring RIB on Cisco IOS XR Software

How to Deploy and Monitor RIB

RC-198

Cisco IOS XR Routing Configuration Guide

How to Deploy and Monitor RIB

To deploy and monitor RIB, you must understand the following concepts:

•Verifying RIB Configuration Using the Routing Table, page RC-198 (required)

•Verifying Networking and Routing Problems, page RC-198 (required)

Verifying RIB Configuration Using the Routing Table

This task verifies the RIB configuration to ensure that RIB is running on the RP and functioning properly

by checking the routing table summary and details.

SUMMARY STEPS

1. show route [afi-all | ipv4 | ipv6] [unicast | multicast | safi-all] summary

2. show route [protocol [process-id]] [afi-all | ipv4 | ipv6] [unicast | multicast | safi-all] [ip-address

[mask]]

DETAILED STEPS

Verifying Networking and Routing Problems

This task verifies the operation of the routes between nodes.

SUMMARY STEPS

1. show route [protocol [instance]] [afi-all | ipv4 | ipv6] [unicast | multicast | safi-all] [ip-address

[mask]]

2. show route [afi-all | ipv4 | ipv6] [unicast | multicast | safi-all] backup [ip-address]

3. show route [afi-all | ipv4 | ipv6] [unicast | multicast | safi-all] best-local ip-address

4. show route [afi-all | ipv4 | ipv6] [unicast | multicast | safi-all] connected

Command or Action Purpose

Step 1 show route [afi-all | ipv4 | ipv6] [unicast |

multicast | safi-all] summary

Example:

RP/0/RP0/CPU0:router# show route summary

Displays route summary information on the specified

routing table.

•The default table summarized is the IPv4 unicast

routing table.

Step 2 show route [protocol [

process-id

]] [afi-all |

ipv4 | ipv6] [unicast | multicast | safi-all]

[ip-ad

dress

[

mask

]]

Example:

RP/0/RP0/CPU0:router# show route ipv4 unicast

Displays more detailed route information on the specified

routing table.

•This command is usually issued with an IP address or

other optional filters to limit its display. Otherwise, it

displays all routes from the default IPv4 unicast routing

table, which can result in an extensive list, depending

on the configuration of the network.

Implementing and Monitoring RIB on Cisco IOS XR Software

How to Deploy and Monitor RIB

RC-199

Cisco IOS XR Routing Configuration Guide

5. show route [afi-all | ipv4 | ipv6] [unicast | multicast | safi-all] local [interface]

6. show route [afi-all | ipv4 | ipv6] [unicast | multicast | safi-all] ip-address mask longer-prefixes

7. show route [afi-all | ipv4 | ipv6] [unicast | multicast | safi-all] next-hop ip-address

DETAILED STEPS

Command or Action Purpose

Step 1 show route [

protocol

[

instance

]] [afi-all |

ipv4 | ipv6] [unicast | multicast | safi-all]

[

ip-address

[

mask

]]

Example:

RP/0/RP0/CPU0:router# show route list list1 bgp

aspo ipv4 unicast 192.168.111/8

Displays the current routes in RIB.

Step 2 show route [afi-all | ipv4 | ipv6] [unicast |

multicast | safi-all] backup [

ip-address

]

Example:

RP/0/RP0/CPU0:router# show route ipv4 unicast

backup 192.168.111/8

Displays backup routes in RIB.

Step 3 show route [afi-all | ipv4 | ipv6] [unicast |

multicast | safi-all] best-local

ip-address

Example:

RP/0/RP0/CPU0:router# show route ipv4 unicast

best-local 192.168.111/8

Displays the best-local address to use for return packets

from the given destination.

Step 4 show route [afi-all | ipv4 | ipv6] [unicast |

multicast | safi-all] connected

Example:

RP/0/RP0/CPU0:router# show route ipv4 unicast

connected

Displays the current connected routes of the routing table.

Step 5 show route [afi-all | ipv4 | ipv6] [unicast |

multicast | safi-all] local [

interface

]

Example:

RP/0/RP0/CPU0:router# show route ipv4 unicast

local

Displays local routes for receive entries in the routing table.

Implementing and Monitoring RIB on Cisco IOS XR Software

Configuration Examples for RIB Monitoring

RC-200

Cisco IOS XR Routing Configuration Guide

Configuration Examples for RIB Monitoring

RIB is not configured separately for the Cisco IOS XR system. RIB computes connectivity of the router

with other nodes in the network based on input from the routing protocols. RIB may be used to monitor

and troubleshoot the connections between RIB and its clients, but it is essentially used to monitor routing

connectivity between the nodes in a network. This section contains displays from the show commands

used to monitor that activity. The following sample output is provided:

•Output of show route Command: Example, page RC-200

•Output of show route backup Command: Example, page RC-201

•Output of show route best-local Command: Example, page RC-201

•Output of show route connected Command: Example, page RC-201

•Output of show route local Command: Example, page RC-201

•Output of show route longer-prefixes Command: Example, page RC-202

•Output of show route next-hop Command: Example, page RC-202

Output of show route Command: Example

The following is sample output from the show route command when entered without an address:

RP/0/RP0/CPU0:router# show route

Codes: C - connected, S - static, I - IGRP, R - RIP, M - mobile, B - BGP

O - OSPF, IA - OSPF inter area, N1 - OSPF NSSA external type 1

N2 - OSPF NSSA external type 2, E1 - OSPF external type 1

E2 - OSPF external type 2, E - EGP, i - ISIS, L1 - IS-IS level-1

L2 - IS-IS level-2, ia - IS-IS inter area

su - IS-IS summary null, * - candidate default

U - per-user static route, o - ODR, L - local

Gateway of last resort is 172.23.54.1 to network 0.0.0.0

C 10.2.210.0/24 is directly connected, 1d21h, Ethernet0/1/0/0

L 10.2.210.221/32 is directly connected, 1d21h, Ethernet0/1/1/0

C 172.20.16.0/24 is directly connected, 1d21h, ATM4/0.1

Step 6 show route [afi-all | ipv4 | ipv6] [unicast |

multicast | safi-all] ip-address

mask

longer-prefixes

Example:

RP/0/RP0/CPU0:router# show route ipv4 unicast

192.168.111/8 longer-prefixes

Displays the current routes in RIB that share a given

number of bits with a given network.

Step 7 show route [afi-all | ipv4 | ipv6] [unicast |

multicast | safi-all] next-hop

ip-address

Example:

RP/0/RP0/CPU0:router# show route ipv4 unicast

next-hop 192.168.1.34

Displays the next hop gateway or host to a destination

address.

Command or Action Purpose

Implementing and Monitoring RIB on Cisco IOS XR Software

Configuration Examples for RIB Monitoring

RC-201

Cisco IOS XR Routing Configuration Guide

L 172.20.16.1/32 is directly connected, 1d21h, ATM4/0.1

C 10.6.100.0/24 is directly connected, 1d21h, Loopback1

L 10.6.200.21/32 is directly connected, 1d21h, Loopback0

S 192.168.40.0/24 [1/0] via 172.20.16.6, 1d21h

Output of show route backup Command: Example

The following is sample output from the show route backup command:

RP/0/RP0/CPU0:router# show route backup

Codes: C - connected, S - static, I - IGRP, R - RIP, M - mobile, B - BGP

O - OSPF, IA - OSPF inter area, N1 - OSPF NSSA external type 1

N2 - OSPF NSSA external type 2, E1 - OSPF external type 1

E2 - OSPF external type 2, E - EGP, i - ISIS, L1 - IS-IS level-1

L2 - IS-IS level-2, ia - IS-IS inter area

su - IS-IS summary null, * - candidate default

U - per-user static route, o - ODR, L - local

S 172.73.51.0/24 is directly connected, 2d20h, GigabitEthernet2/2

Backup O E2 [110/1] via 10.12.12.2, POS3/0

Output of show route best-local Command: Example

The following is sample output from the show route best-local command:

RP/0/RP0/CPU0:router# show route best-local 10.12.12.1

Routing entry for 10.12.12.1/32

Known via "local", distance 0, metric 0 (connected)

Routing Descriptor Blocks

10.12.12.1 directly connected, via POS3/0

Route metric is 0

Output of show route connected Command: Example

The following is sample output from the show route connected command:

RP/0/RP0/CPU0:router# show route connected

Gateway of last resort is 172.23.54.1 to network 0.0.0.0

C 10.2.210.0/24 is directly connected, 1d21h, Ethernet0

C 172.20.16.0/24 is directly connected, 1d21h, ATM4/0.1

C 10.6.100.0/24 is directly connected, 1d21h, Loopback1

Output of show route local Command: Example

The following is sample output from the show route local command:

RP/0/RP0/CPU0:router# show route local

L 10.10.10.1/32 is directly connected, 00:14:36, Loopback0

L 10.91.36.98/32 is directly connected, 00:14:32, Ethernet0/0

L 172.22.12.1/32 is directly connected, 00:13:35, POS3/0

Implementing and Monitoring RIB on Cisco IOS XR Software

Where to Go Next

RC-202

Cisco IOS XR Routing Configuration Guide

L 192.168.20.2/32 is directly connected, 00:13:27, GigabitEthernet2/0

L 10.254.254.1/32 is directly connected, 00:13:26, GigabitEthernet2/2

Output of show route longer-prefixes Command: Example

The following is sample output from the show route longer-prefixes command:

RP/0/RP0/CPU0:router# show route ipv4 172.16.0.0/8 longer-prefixes

Codes: C - connected, S - static, I - IGRP, R - RIP, M - mobile, B - BGP

O - OSPF, IA - OSPF inter area, N1 - OSPF NSSA external type 1

N2 - OSPF NSSA external type 2, E1 - OSPF external type 1

E2 - OSPF external type 2, E - EGP, i - ISIS, L1 - IS-IS level-1

L2 - IS-IS level-2, ia - IS-IS inter area

su - IS-IS summary null, * - candidate default

U - per-user static route, o - ODR, L - local

Gateway of last resort is 172.23.54.1 to network 0.0.0.0

S 172.16.2.0/32 is directly connected, 00:00:24, Loopback0

S 172.16.3.0/32 is directly connected, 00:00:24, Loopback0

S 172.16.4.0/32 is directly connected, 00:00:24, Loopback0

S 172.16.5.0/32 is directly connected, 00:00:24, Loopback0

S 172.16.6.0/32 is directly connected, 00:00:24, Loopback0

S 172.16.7.0/32 is directly connected, 00:00:24, Loopback0

S 172.16.8.0/32 is directly connected, 00:00:24, Loopback0

S 172.16.9.0/32 is directly connected, 00:00:24, Loopback0

Output of show route next-hop Command: Example

The following is sample output from the show route next-hop command:

RP/0/RP0/CPU0:router# show route next-hop 10.0.0.1

Routing entry for 10.0.0.0/24

Known via "connected", distance 0, metric 0 (connected)

Routing Descriptor Blocks

10.0.0.50 directly connected, via GigabitEthernet6/0

Route metric is 0

Where to Go Next

For additional information on the protocols that interact with RIB, you may want to see the following

publications:

•Implementing BGP on Cisco IOS XR Software

•Implementing IS-IS on Cisco IOS XR Software

•Implementing OSPF on Cisco IOS XR Software

•RIB Commands on Cisco IOS XR Software

Implementing and Monitoring RIB on Cisco IOS XR Software

Additional References

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Additional References

The following sections provide references related to implementing RIB on Cisco IOS XR software:

Related Documents

Standards

MIBs

Related Topic Document Title

Routing Information Base commands: complete

command syntax, command modes, command history,

defaults, usage guidelines, and examples

RIB Commands on Cisco IOS XR Software in the Cisco IOS XR

Routing Command Reference, Release 3.2

BGP commands: complete command syntax, command

modes, command history, defaults, usage guidelines,

and examples

BGP Commands on Cisco IOS XR Software, in the Cisco IOS XR

Routing Command Reference, Release 3.2

IS-IS commands: complete command syntax,

command modes, command history, defaults, usage

guidelines, and examples

IS-IS Commands on Cisco IOS XR Software in the Cisco IOS XR

Routing Command Reference, Release 3.2

OSPF commands: complete command syntax,

command modes, command history, defaults, usage

guidelines, and examples

OSPF Commands on Cisco IOS XR Software in the Cisco IOS XR

Routing Command Reference, Release 3.2

OSPFv3 commands: complete command syntax,

command modes, command history, defaults, usage

guidelines, and examples

OSPFv3 Commands on Cisco IOS XR Software in the Cisco IOS XR

Routing Command Reference, Release 3.2

Multicast commands: complete command syntax,

command modes, command history, defaults, usage

guidelines, and examples

Cisco IOS XR Multicast Command Reference, Release 3.2

Multicast configuration: complete command syntax,

command modes, command history, defaults, usage

guidelines, and examples

Cisco IOS XR Multicast Configuration Guide, Release 3.2

Standards Title

No new or modified standards are supported by this

feature, and support for existing standards has not been

modified by this feature.

—

MIBs MIBs Link

•IP-FORWARD-MIB

•RFC1213-MIB

To locate and download MIBs for selected platforms using

Cisco IOS XR software, use the Cisco MIB Locator found at the

following URL:

http://cisco.com/public/sw-center/netmgmt/cmtk/mibs.shtml

Implementing and Monitoring RIB on Cisco IOS XR Software

Additional References

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Cisco IOS XR Routing Configuration Guide

RFCs

Technical Assistance

RFCs Title

No new or modified RFCs are supported by this

feature, and support for existing RFCs has not been

modified by this feature.

—

Description Link

The Cisco Technical Support website contains

thousands of pages of searchable technical content,

including links to products, technologies, solutions,

technical tips, and tools. Registered Cisco.com users

can log in from this page to access even more content.

http://www.cisco.com/techsupport

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Implementing Routing Policy on Cisco IOS XR

Software

A routing policy instructs the router to inspect routes, filter them, and potentially modify their attributes

as they are accepted from a peer, advertised to a peer, or redistributed from one routing protocol to

another. Routing protocols make decisions to advertise, aggregate, discard, distribute, export, hold,

import, redistribute and otherwise modify routes based on configured routing policy.

The routing policy language (RPL) has been designed to provide a single, straightforward language in

which all routing policy needs can be expressed. RPL was designed to support large-scale routing

configurations. It greatly reduces the redundancy inherent in previous routing policy configuration

methods. RPL has been designed to streamline routing policy configuration, to reduce system resources

required to store and process these configurations, and to simplify troubleshooting.

Note For more information about routing policy on the Cisco IOS XR software and complete descriptions of

the routing policy commands listed in this module, see the “Related Documents” section of this module.

To locate documentation for other commands that might appear during execution of a configuration task,

search online in the Cisco IOS XR software master command index.

Feature History for Implementing Routing Policy on Cisco IOS XR Software

Contents

•Prerequisites for Implementing Routing Policy, page RC-206

•Information About Implementing Routing Policy, page RC-206

•How to Implement Routing Policy, page RC-237

•Configuration Examples for Implementing Routing Policy, page RC-241

•Additional References, page RC-244

Release Modification

Release 2.0 This feature was introduced on the Cisco CRS-1.

Release 3.0 No modification.

Release 3.2 Support was added for the Cisco XR 12000 Series Router.

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Prerequisites for Implementing Routing Policy

The following are prerequisites for implementing Routing Policy on Cisco IOS XR Software:

•To use this command, you must be in a user group associated with a task group that includes the

proper task IDs. For detailed information about user groups and task IDs, see the Configuring AAA

Services on Cisco IOS XR Software module of the Cisco IOS XR System Security Configuration

Guide.

•Border Gateway Protocol (BGP), integrated Intermediate System-to-Intermediate System (IS-IS),

or Open Shortest Path First (OSPF) must be configured in your network.

Information About Implementing Routing Policy

To implement RPL, you need to understand the following concepts:

•Routing Policy Language, page RC-206

•Routing Policy Configuration Basics, page RC-213

•Policy Definitions, page RC-213

•Parameterization, page RC-214

•Semantics of Policy Application, page RC-215

•Policy Statements, page RC-219

•Attach Points, page RC-223

•Attached Policy Modification, page RC-235

•Nonattached Policy Modification, page RC-235

Routing Policy Language

This section contains the following information:

•Routing Policy Language Overview, page RC-206

•Routing Policy Language Structure, page RC-207

•Routing Policy Language Components, page RC-211

•Routing Policy Language Usage, page RC-211

Routing Policy Language Overview

RPL was developed to support large-scale routing configurations. RPL has several fundamental

capabilities that differ from those present in configurations oriented to traditional route maps, access

lists, and prefix lists. The first of these capabilities is the ability to build policies in a modular form.

Common blocks of policy can be defined and maintained independently. These common blocks of policy

can then be applied from other blocks of policy to build complete policies. This capability reduces the

amount of configuration information that needs to be maintained. In addition, these common blocks of

policy can be parameterized. This parameterization allows for policies that share the same structure but

differ in the specific values that are set or matched against to be maintained as independent blocks of

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policy. For example, three policies that are identical in every way except for the local preference value

they set can be represented as one common parameterized policy that takes the varying local preference

value as a parameter to the policy.

The policy language introduces the notion of sets. Sets are containers of similar data that can be used in

route attribute matching and setting operations. Four set types exist: prefix-sets, community-sets,

as-path-sets, and extcommunity-sets. These sets hold groupings of IPv4 or IPv6 prefixes, community

values, AS path regular expressions, and extended community values, respectively. Sets are simply

containers of data. Most sets also have an inline variant. An inline set allows for small enumerations of

values to be used directly in a policy rather than having to refer to a named set. Prefix lists, community

lists, and AS path lists must be maintained even when only one or two items are in the list. An inline set

in RPL allows the user to place small sets of values directly in the policy body without having to refer

to a named set.

Decision making, such as accept and deny, is explicitly controlled by the policy definitions themselves.

RPL combines matching operators, which may use set data, with the traditional Boolean logic operators

and, or, and not into complex conditional expressions. All matching operations return a true or false

result. The execution of these conditional expressions and their associated actions can then be controlled

by using simple if then, elseif, and else structures, which allow the evaluation paths through the policy

to be fully specified by the user.

Routing Policy Language Structure

This section describes the basic structure of RPL.

Names

The policy language provides two kinds of persistent, namable objects: sets and policies. Definition of

these objects is bracketed by beginning and ending command lines. For example, to define a policy

named test, the configuration syntax would look similar to the following:

route-policy test

[ . . . policy statements . . . ]

end-policy

Legal names for policy objects can be any sequence of the upper- and lowercase alphabetic characters;

the numerals 0 to 9; and the punctuation characters period, hyphen, and underscore. A name must begin

with a letter or numeral.

Sets

In this context, the term set is used in its mathematical sense to mean an unordered collection of unique

elements. The policy language provides sets as a container for groups of values for matching purposes.

Sets are used in conditional expressions. The elements of the set are separated by commas. Null (empty)

sets are not allowed.

Four kinds of sets exist: as-path-set, community-set, extcommunity-set, and prefix-set. You may want to

perform comparisons against a small number of elements, such as two or three community values, for

example. To allow for these comparisons, the user can enumerate these values directly. These

enumerations are referred to as inline sets. Functionally, inline sets are equivalent to named sets, but

allow for simple tests to be inline. Thus, comparisons do not require that a separate named set be

maintained when only one or two elements are being compared. See the set types described in the

following sections for the syntax. In general, the syntax for an inline set is a comma-separated list

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surrounded by parentheses as follows: (<element-entry>,<element-entry>,<element-entry>,

...<element-entry>), where <element-entry> is an entry of an item appropriate to the type of usage such

as a prefix or a community value.

The following is an example using an inline community set:

route-policy sample-inline

if community matches-any ([10..15]:100) then

set local-preference 100

endif

end-policy

The following is an equivalent example using the named set test-communities:

community-set test-communities

10:100,

11:100,

12:100,

13:100,

14:100,

15:100

end-set

route-policy sample

if community matches-any test-communities then

set local-preference 100

endif

end-policy

Both of these policies are functionally equivalent, but the inline form does not require the configuration

of the community set just to store the six values. You can choose the form appropriate to the

configuration context. In the following sections, examples of both the named set version and the inline

form are provided where appropriate.

as-path-set

An AS path set comprises operations for matching an AS path attribute. The only matching operation is

a regular expression match.

Named Set Form

The named set form uses the ios-regex keyword to indicate the type of regular expression and requires

single quotation marks around the regular expression.

The following is a sample definition of a named AS path set:

as-path-set aset1

ios-regex ’_42$’,

ios-regex ’_127$’

end-set

This AS path set comprises two elements. When used in a matching operation, this AS path set matches

any route whose AS path ends with either the autonomous system (AS) number 42 or 127.

To remove the named AS path set, use the no as-path-set aset1 command-line interface (CLI) command.

Inline Set Form

The inline set form is a parenthesized list of comma-separated expressions, as follows:

(ios-regex '_42$', ios-regex '_127$')

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This set matches the same AS paths as the previously named set, but does not require the extra effort of

creating a named set separate from the policy that uses it.

community-set

A community-set holds community values for matching against the BGP community attribute. A

community is a 32-bit quantity. Integer community values must be split in half and expressed as two

unsigned decimal integers in the range from 0 to 65535, separated by a colon. Single 32-bit community

values are not allowed. The following is the named set form:

Named Set Form

community-set cset1

12:34,

12:56,

12:78,

internet

end-set

Inline Set Form

(12:34, 12:56, 12:78)

($as:34, $as:$tag1, 12:78, internet)

The inline form of a community-set also supports parameterization. Each 16-bit portion of the

community may be parameterized. See the “Parameterization” section on page RC-214 for more

information.

RPL provides symbolic names for the standard well-known community values: internet is 0:0, no-export

is 65535:65281, no-advertise is 65535:65282, and local-as is 65535:65283.

RPL also provides a facility for using wildcards in community specifications. A wildcard is specified by

inserting an asterisk (*) in place of one of the 16-bit portions of the community specification; the

wildcard indicates that any value for that portion of the community matches. Thus, the following policy

matches all communities in which the autonomous system part of the community is 123:

community-set cset3

123:*

end-set

Every community set must contain at least one community value. Empty community sets are invalid and

are rejected.

extcommunity-set

An extended community-set is analogous to a community-set except that it contains extended

community values instead of regular community values. It also supports named forms and inline forms.

The following are syntactic examples:

Named Form

extcommunity-set extcomm-set1

RT:1.2.3.4:666,

RT:1234:666,

SoO:1.2.3.4:777,

SoO :4567:777

end-set

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Inline Form

(RT:1.2.3.4:666, RT:1234:6667, SoO:1.2.3.4:777, SoO:45678:777)

(RT:$ipaddr:666, RT:1234:$tag, SoO:1.2.3.4:777, SoO:$tag2:777)

As with community sets, the inline form supports parameterization within parameterized policies. Either

portion of the extended community value can be parameterized.

Every extended community-set must contain at least one extended community value. Empty extended

community-sets are invalid and rejected.

prefix-set

A prefix-set holds IPv4 or IPv6 prefix match specifications, each of which has four parts: an address, a

mask length, a minimum matching length, and a maximum matching length. The address is required, but

the other three parts are optional. The address is a standard dotted-decimal IPv4 or colon-separated

hexadecimal IPv6 address. The mask length, if present, is a nonnegative decimal integer in the range

from 0 to 32 (0 to 128 for IPv6) following the address and separated from it by a slash. The optional

minimum matching length follows the address and optional mask length and is expressed as the keyword

ge (mnemonic for greater than or equal to), followed by a nonnegative decimal integer in the range from

0 to 32 (0 to 128 for IPv6). The optional maximum matching length follows the rest and is expressed by

the keyword le (mnemonic for less than or equal to), followed by yet another nonnegative decimal integer

in the range from 0 to 32 (0 to 128 for IPv6). A syntactic shortcut for specifying an exact length for

prefixes to match is the eq keyword (mnemonic for equal to).

If a prefix match specification has no mask length, then the default mask length is 32 for IPv4 and 128

for IPv6. The default minimum matching length is the mask length. If a minimum matching length is

specified, then the default maximum matching length is 32 for IPv4 and 128 for IPv6. Otherwise, if

neither minimum nor maximum is specified, the default maximum is the mask length.

The prefix-set itself is a comma-separated list of prefix match specifications. The following are

examples:

prefix-set legal-ipv4-prefix-examples

10.0.1.1,

10.0.2.0/24,

10.0.3.0/24 ge 28,

10.0.4.0/24 le 28,

10.0.5.0/24 ge 26 le 30,

10.0.6.0/24 eq 28

end-set

prefix-set legal-ipv6-prefix-examples

2001:0:0:1::/64,

2001:0:0:2::/64 ge 96,

2001:0:0:2::/64 ge 96 le 100,

2001:0:0:2::/64 eq 100

end-set

The first element of the prefix-set matches only one possible value, 10.0.1.1/32 or the host address

10.0.1.1. The second element matches only one possible value, 10.0.2.0/24. The third element matches

a range of prefix values, from 10.0.3.0/28 to 10.0.3.255/32. The fourth element matches a range of

values, from 10.0.4.0/24 to 10.0.4.240/28. The fifth element matches prefixes in the range from

10.0.5.0/26 to 10.0.5.252/30. The sixth element matches any prefix of length 28 in the range from

10.0.6.0/28 through 10.0.6.240/28.

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The following prefix-set consists entirely of invalid prefix match specifications:

prefix-set ILLEGAL-PREFIX-EXAMPLES

10.1.1.1 ge 16,

10.1.2.1 le 16,

10.1.3.0/24 le 23,

10.1.4.0/24 ge 33,

10.1.5.0/25 ge 29 le 28

end-set

Neither the minimum length nor maximum length is valid without a mask length. The maximum length

must be at least the mask length. For IPv4, the minimum length must be less than 32, the maximum

length of an IPv4 prefix. For IPv6, the minimum length must be less than 128, the maximum length of

an IPv6 prefix. The maximum length must be equal to or greater than the minimum length.

Routing Policy Language Components

Four main components in the routing policy language are involved in defining, modifying, and using

policies: the configuration front end, policy repository, execution engine, and policy clients themselves.

The configuration front end (CLI) is the mechanism to define and modify policies. This configuration is

then stored on the router using the normal storage means and can be displayed using the normal

configuration show commands.

The second component of the policy infrastructure, the policy repository, has several responsibilities.

First, it compiles the user-entered configuration into a form that the execution engine can understand.

Second, it performs much of the verification of policies; and it ensures that defined policies can actually

be executed properly. Third, it tracks which attach points are using which policies so that when policies

are modified the appropriate clients are properly updated with the new policies relevant to them.

The third component is the execution engine. This component is the piece that actually runs policies as

the clients request. The process can be thought of as receiving a route from one of the policy clients and

then executing the actual policy against the specific route data.

The fourth component is the policy clients (the routing protocols). This component calls the execution

engine at the appropriate times to have a given policy be applied to a given route, and then perform some

number of actions. These actions may include deleting the route if policy indicated that it should be

dropped, passing along the route to the protocol decision tree as a candidate for the best route, or

advertising a policy modified route to a neighbor or peer as appropriate.

Routing Policy Language Usage

This section provides basic routing policy language usage examples. See the “How to Implement

Routing Policy” section on page RC-237 for detailed information on how to implement routing policy

language.

The pass policy

The following example shows how the policy accepts all presented routes without modifying the routes.

route-policy quickstart-pass

pass

end-policy

The drop everything policy

The following example shows how the policy explicitly rejects all routes presented to it. This type of

policy is used to ignoring everything coming from a misbehaving peer.

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route-policy quickstart-drop

drop

end-policy

Ignore routes with specific AS numbers in the path

The following example shows the policy definition in three parts. First, the as-path-set command

defines three regular expressions to match against an AS path. Second, the route-policy command

applies the AS path set to a route. If the AS path attribute of the route matches the regular expression

defined with the as-path-set command, the protocol refuses the route. Third, the route policy is attached

to BGP neighbor 10.0.1.2. BGP consults the policy named ignore_path_as on routes received (imported)

from neighbor 10.0.1.2.

as-path-set ignore_path

ios-regex '_11_',

ios-regex '_22_',

ios-regex '_33_'

end-set

route-policy ignore_path_as

if as-path in ignore_path then

drop

else

pass

endif

end-policy

router bgp 2

neighbor 10.0.1.2 address-family ipv4 unicast policy ignore_path_as in

Set community based on MED

The following example shows how the policy tests the MED of a route and modifies the community

attribute of the route based on the value of the MED. If the MED value is 127, the policy adds the

community 123:456 to the route. If the MED value is 63, the policy adds the value 123:789 to the

community attribute of the route. Otherwise, the policy removes the community 123:123 from the route.

In any case, the policy instructs the protocol to accept the route.

route-policy quickstart-med

if med eq 127 then

set community (123:456) additive

elseif med eq 63 then

set community (123:789) additive

else

delete community in (123:123)

endif

pass

end-policy

Set local preference based on community

The following example shows how the community-set named quickstart-communities defines

community values. The route policy named quickstart-localpref tests a route for the presence of the

communities specified in the quickstart-communities community set. If any of the community values are

present in the route, the route policy sets the local preference attribute of the route to 31. In any case, the

policy instructs the protocol to accept the route.

community-set quickstart-communities

987:654,

987:543,

987:321,

987:210

end-set

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route-policy quickstart-localpref

if community matches-any quickstart-communities then

set local-preference 31

endif

pass

end-policy

Persistent Remarks

The following example shows how comments are placed in the policy to clarify the meaning of the

entries in the set and the statements in the policy. The remarks are persistent, meaning they remain

attached to the policy. For example, remarks are displayed in the output of the show running-config

command. Adding remarks to the policy makes the policy easier to understand, modify at a later date,

and troubleshoot if an unexpected behavior occurs.

prefix-set rfc1918

# These are the networks defined as private in RFC1918 (including

# all subnets thereof)

10.0.0.0/8 ge 8,

172.16.0.0/12 ge 12,

192.168.0.0/16 ge 16

end-set

route-policy quickstart-remarks

# Handle routes to RFC1918 networks

if destination in rfc1918 then

# Set the community such that we do not export the route

set community (no-export) additive

endif

end-policy

Routing Policy Configuration Basics

Route policies comprise series of statements and expressions that are bracketed with the route-policy

and end-policy keywords. Rather than a collection of individual commands (one for each line), the

statements within a route policy have context relative to each other. Thus, instead of each line being an

individual command, each policy or set is an independent configuration object that can be used, entered,

and manipulated as a unit.

Each line of a policy configuration is a logical subunit. At least one new line must follow the then, else,

and end-policy keywords. A new line must also follow the closing parenthesis of a parameter list and

the name string in a reference to an AS path set, community set, extended community set, or prefix set.

At least one new line must precede the definition of a route policy, AS path set, community set, extended

community set, or prefix set. One or more new lines can follow an action statement. One or more new

lines can follow a comma separator in a named AS path set, community set, extended community set, or

prefix set. A new line must appear at the end of a logical unit of policy expression and may not appear

anywhere else.

Policy Definitions

Policy definitions create named sequences of policy statements. A policy definition consists of the CLI

route-policy keyword followed by a name, a sequence of policy statements, and the end-policy

keyword. For example, the following policy drops any route it encounters:

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route-policy drop-everything

drop

end-policy

The name serves as a handle for binding the policy to protocols. To remove a policy definition, issue the

no route-policy name command.

Policies may also refer to other policies such that common blocks of policy can be reused. This reference

to other policies is accomplished by using the apply statement, as shown in the following example:

route-policy check-as-1234

if as-path passes-through ‘1234’ then

apply drop-everything

else

pass

endif

end-policy

The apply statement indicates that the policy drop-everything should be executed if the route under

consideration passed through autonomous system 1234 before it is received. If a route that has

autonomous system 1234 in its AS path is received, the route is dropped; otherwise, the route is accepted

without modification. This policy is an example of a hierarchical policy. Thus, the semantics of the apply

statement are just as if the applied policy were cut and pasted into the applying policy:

route-policy check-as-1234-prime

if as-path passes-through '1234' then

drop

else

pass

endif

end-policy

You may have as many levels of hierarchy as desired. However, many levels may be difficult to maintain

and understand.

Parameterization

In addition to supporting reuse of policies using the apply statement, policies can be defined that allow

for parameterization of some of the attributes. The following example shows how to define a

parameterized policy named param-example. In this case, the policy takes one parameter, $mytag.

Parameters always begin with a dollar sign and consist otherwise of any alphanumeric characters.

Parameters can be substituted into any attribute that takes a parameter.

In the following example, a 16-bit community tag is used as a parameter:

route-policy param-example ($mytag)

set community (1234:$mytag) additive

end-policy

This parameterized policy can then be reused with different parameterizations, as shown in the following

example. In this manner, policies that share a common structure but use different values in some of their

individual statements can be modularized. For details on which attributes can be parameterized, see the

individual attribute sections.

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route-policy origin-10

if as-path originates-from ‘10’ then

apply param-example(10)

else

pass

endif

end-policy

route-policy origin-20

if as-path originates-from ‘20’ then

apply param-example(20)

else

pass

endif

end-policy

The parameterized policy param-example provides a policy definition that is expanded with the values

provided as the parameters in the apply statement. Note that the policy hierarchy is always maintained,

Thus, if the definition of param-example changes, then the behavior of origin_10 and origin_20 changes

to match.

The effect of the origin-10 policy is that it adds the community 1234:10 to all routes that pass through

this policy and have an AS path indicating the route originated from autonomous system 10. The

origin-20 policy is similar except that it adds to community 1234:20 for routes originating from

autonomous system 20.

Semantics of Policy Application

This section discusses how routing policies are evaluated and applied. The following concepts are

discussed:

•Boolean Operator Precedence, page RC-215

•Multiple Modifications of the Same Attribute, page RC-216

•When Attributes Are Modified, page RC-216

•Default Drop Disposition, page RC-217

•Control Flow, page RC-217

•Policy Verification, page RC-218

Boolean Operator Precedence

Boolean expressions are evaluated in order of operator precedence, from left to right. The highest

precedence operator is not, followed by and, and then or. The following expression:

med eq 10 and not destination in (10.1.3.0/24) or community matches-any ([10..25]:35)

if fully parenthesized to display the order of evaluation, would look like this:

(med eq 10 and (not destination in (10.1.3.0/24))) or community matches-any ([10..25]:35)

The inner not applies only to the destination test; the and combines the result of the not expression with

the Multi Exit Discriminator (MED) test; and the or combines that result with the community test. If the

order of operations are rearranged:

not med eq 10 and destination in (10.1.3.0/24) or community matches-any ([10..25]:35)

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then the expression, fully parenthesized, would look like the following:

((not med eq 10) and destination in (10.1.3.0/24)) or community matches-any ([10..25]:35)

Multiple Modifications of the Same Attribute

When a policy replaces the value of an attribute multiple times, the last assignment wins because all

actions are executed. Because the MED attribute in BGP is one unique value, the last value to which it

gets set to wins. Therefore, the following policy results in a route with a MED value of 12:

set med 9

set med 10

set med 11

set med 12

This example is trivial, but the feature is not. It is possible to write a policy that effectively changes the

value for an attribute. For example:

set med 8

if community matches-any cs1 then

set local-preference 122

if community matches-any cs2 then

set med 12

endif

The result is a route with a MED of 8, unless the community list of the route matches both cs1 and cs2,

in which case the result is a route with a MED of 12.

In the case in which the attribute being modified can contain only one value, it is easy to think of this

case as the last statement wins. However, a few attributes can contain multiple values and the result of

multiple actions on the attribute is cumulative rather than as a replacement. The first of these cases is the

use of the additive keyword on community and extended community evaluation. Consider a policy of

the form:

route-policy community-add

set community (10:23)

set community (10:24) additive

set community (10:25) additive

end-policy

This policy sets the community string on the route to contain all three community values: 10:23, 10:24,

and 10:25.

The second of these cases is AS path prepending. Consider a policy of the form:

route-policy prepend-example

prepend as-path 2 3

prepend as-path 666 2

end-policy

This policy prepends the following to the AS path (666 666 2 2 2). This prepending is a result of all

actions being taken and to AS path being an attribute that contains an array of values rather than a simple

scalar value.

When Attributes Are Modified

A policy does not modify route attribute values until all tests have been completed. In other words,

comparison operators always run on the initial data in the route. Intermediate modifications of the route

attributes do not have a cascading effect on the evaluation of the policy. Take the following example:

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if med eq 12 then

set med 42

if med eq 42 then

drop

endif

This policy never executes the drop statement because the second test (med eq 42) sees the original,

unmodified value of the MED in the route. Because the MED has to be 12 to get to the second test, the

second test always returns false.

Default Drop Disposition

All route policies have a default action to drop the route under evaluation unless the route has been

modified by a policy action or explicitly passed. Applied (nested) policies implement this disposition as

though the applied policy were pasted into the point where it is applied.

Consider a policy to allow all routes in the 10 network and set their local preference to 200 while

dropping all other routes. You might write the policy as follows:

route-policy two

if destination in (10.0.0.0/8 ge 8 le 32) then

set local-preference 200

endif

end-policy

route-policy one

apply two

end-policy

It may appear that policy one drops all routes because it neither contains an explicit pass statement nor

modifies a route attribute. However, the applied policy does set an attribute for some routes and this

disposition is passed along to policy one. The result is that policy one passes routes with destinations in

network 10, and drops all others.

Control Flow

Policy statements are processed sequentially in the order in which they appear in the configuration.

Policies that hierarchically reference other policy blocks are processed as if the referenced policy blocks

had been directly substituted inline. For example, if the following policies are defined:

route-policy one

set weight 100

end-policy

route-policy two

set med 200

end-policy

route-policy three

apply two

set community (2:666) additive

end-policy

route-policy four

apply one

apply three

pass

end-policy

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Policy four could be rewritten in an equivalent way as follows:

route-policy four-equivalent

set weight 100

set med 200

set community (2:666) additive

pass

end-policy

Note The pass statement is not required and can be removed to represent the equivalent policy in another way.

Policy Verification

Several different types of verification occur when policies are being defined and used.

Range Checking

As policies are being defined, some simple verifications, such as range checking of values, is done. For

example, the MED that is being set is checked to verify that it is in a proper range for the MED attribute.

However, this range checking cannot cover parameter specifications because they may not have defined

values yet. These parameter specifications are verified when a policy is attached to an attach point. The

policy repository also verifies that there are no recursive definitions of policy, and that parameter

numbers are correct. At attach time, all policies must be well formed. All sets and policies that they

reference must be defined and have valid values. Likewise, any parameter values must also be in the

proper ranges.

Incomplete Policy and Set References

As long as a given policy is not attached at an attach point, the policy is allowed to refer to nonexistent

sets and policies, which allows for freedom of workflow. You can build configurations that reference sets

or policy blocks that are not yet defined, and then can later fill in those undefined policies and sets,

thereby achieving much greater flexibility in policy definition. Every piece of policy you want to

reference while defining a policy need not exist in the configuration. Thus, a user can define a policy

sample that references the policy bar using an apply statement even if the policy bar does not exist.

Similarly, a user can enter a policy statement that refers to a nonexistent set.

However, the existence of all referenced policies and sets is enforced when a policy is attached. If you

attempt to attach the policy sample with the reference to an undefined policy bar at an inbound BGP

policy using the neighbor 1.2.3.4 address-family ipv4 unicast policy sample in command, the

configuration attempt is rejected because the policy bar does not exist.

Likewise, you cannot remove a route policy or set that is currently in use at an attach point because this

removal would result in an undefined reference. An attempt to remove a route policy or set that is

currently in use results in an error message to the user.

A condition exists that is referred to as a null policy in which the policy bar exists but has no statements,

actions, or dispositions in it. In other words, the policy bar does exist as follows:

route-policy bar

end-policy

This is a valid policy block. It effectively forces all routes to be dropped because it is a policy block that

never modifies a route, nor does it include the pass statement. Thus, the default action of drop for the

policy block is followed.

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Attached Policy Modification

Policies that are in use do, on occasion, need to be modified. Traditionally, configuration changes are

done by completely removing the relevant configuration and then re-entering it. However, this allows for

a window of time in which no policy is attached and the default action takes place. RPL provides a

mechanism for an atomic change so that if a policy is redeclared, or edited using the emacs editor, the

new configuration is applied immediately, which allows for policies that are in use to be changed without

having a window of time in which no policy is applied at the given attach point.

Verification of Attribute Comparisons and Actions

The policy repository knows which attributes, actions, and comparisons are valid at each attach point.

When a policy is attached, these actions and comparisons are verified against the capabilities of that

particular attach point. Take, for example, the following policy definition:

route-policy bad

set med 100

set level level-1-2

set cost 200

end-policy

This policy attempts to perform actions to set the BGP attribute med, IS-IS attribute level, and OSPF

attribute cost. The system allows you to define such a policy, but it does not allow you to attach such a

policy. If you had defined the policy bad and then attempted to attach it as an inbound BGP policy using

the BGP configuration statement neighbor 1.2.3.4 address-family ipv4 unicast route-policy bad in the

system would reject this configuration attempt. This rejection results from the verification process

checking the policy and realizing that while BGP could set the MED, it has no way of setting the level

or cost as the level and cost are attributes of IS-IS and OSPF, respectively. Instead of silently omitting

the actions that cannot be done, the system generates an error to the user. Likewise, a valid policy in use

at an attach point cannot be modified in such a way as to introduce an attempt to modify a nonexistent

attribute or to compare against a nonexistent attribute. The verifiers test for nonexistent attributes and

reject such a configuration attempt.

Policy Statements

Four types of policy statements exist: remark, disposition (drop and pass), action (set), and if

(comparator).

Remark

A remark is text attached to policy configuration but otherwise ignored by the policy language parser.

Remarks are useful for documenting parts of a policy. The syntax for a remark is text that has each line

prepended with a pound sign (#):

# This is a simple one-line remark.

# This

# is a remark

# comprising multiple

# lines.

In general, remarks are used between complete statements or elements of a set. Remarks are not

supported in the middle of statements or within an inline set definition.

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Unlike traditional !-comments in the CLI, RPL remarks persist through reboots and when configurations

are saved to disk or a TFTP server and then loaded back onto the router.

Disposition

By default, a route is dropped at the end of policy processing unless either the policy modifies a route

attribute or it passes the route by means of an explicit pass statement. For example, the following policy

drops all routes because it neither modifies the attribute of any route nor explicitly passes it.

route-policy EMPTY

end-policy

Whereas the following policies pass all routes that they evaluate.

route-policy PASS-ALL

pass

end-policy

route-policy SET-LPREF

set local-preference 200

end-policy

In addition to being implicitly dropped, a route may be dropped by an explicit drop statement. Drop

statements cause a route to be dropped immediately so that no further policy processing is done. Note

also that a drop statement overrides any previously processed pass statements or attribute modifications.

For example, the following policy drops all routes. The first pass statement is executed, but is then

immediately overridden by the drop statement. The second pass statement never gets executed.

route-policy DROP-EXAMPLE

pass

drop

pass

end-policy

When one policy applies another, it is as if the applied policy were copied into the right place in the

applying policy, and then the same drop-and-pass semantics are put into effect. For example, policies

ONE and TWO are equivalent to policy ONE-PRIME:

route-policy ONE

apply route-policy two

if as-path neighbor-is '123' then

pass

endif

end-policy

route-policy TWO

if destination in (10.0.0.0/16 le 32) then

drop

endif

end-policy

route-policy ONE-PRIME

if destination in (10.0.0.0/16 le 32) then

drop

endif

if as-path neighbor-is '123' then

pass

endif

end-policy

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Because the effect of an explicit drop statement is immediate, routes in 10.0.0.0/16 le 32 are dropped

without any further policy processing. Other routes are then considered to see if they were advertised by

autonomous system 123. If they were advertised, they are passed; otherwise, they are implicitly dropped

at the end of all policy processing.

Action

An action is a sequence of primitive operations that modify a route. Most actions, but not all, are

distinguished by the set keyword. In a route policy, actions can be grouped together. For example, the

following is a route policy comprising three actions:

route-policy actions

set med 217

set community (12:34) additive

delete community in (12:56)

end-policy

In its simplest form, an if statement uses a conditional expression to decide which actions or dispositions

should be taken for the given route. For example:

if as-path in as-path-set-1 then

drop

endif

The example indicates that any routes whose AS path is in the set as-path-set-1 are dropped. The contents

of the then clause may be an arbitrary sequence of policy statements.

The following example contains two action statements:

if origin is igp then

set med 42

prepend as-path 73 5

endif

The CLI provides support for the exit command as an alternative to the endif command.

The if statement also permits an else clause, which is executed if the if condition is false:

if med eq 8 then

set community (12:34) additive

else

set community (12:56) additive

endif

The policy language also provides syntax, using the elseif keyword, to string together a sequence of tests:

if med eq 150 then

set local-preference 10

elseif med eq 200 then

set local-preference 60

elseif med eq 250 then

set local-preference 110

else

set local-preference 0

endif

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The statements within an if statement may themselves be if statements, as shown in the following

example:

if community matches-any (12:34,56:78) then

if med eq 150 then

drop

endif

set local-preference 100

endif

This policy example sets the value of the local preference attribute to 100 on any route that has a

community value of 12:34 or 56:78 associated with it. However, if any of these routes has a MED value

of 150, then these routes with either the community value of 12:34 or 56:78 and a MED of 150 are

dropped.

Boolean Conditions

In the previous section describing the if statement, all of the examples use simple Boolean conditions

that evaluate to either true or false. RPL also provides a way to build compound conditions from simple

conditions by means of Boolean operators.

Three Boolean operators exist: negation (not), conjunction (and), and disjunction (or). In the policy

language, negation has the highest precedence, followed by conjunction, and then by disjunction.

Parentheses may be used to group compound conditions to override precedence or to improve

readability.

The following simple condition:

med eq 42

is true only if the value of the MED in the route is 42, otherwise it is false.

A simple condition may also be negated using the not operator:

not next-hop in (10.0.2.2)

Any Boolean condition enclosed in parentheses is itself a Boolean condition:

(destination in prefix-list-1)

A compound condition takes either of two forms. It can be a simple expression followed by the and

operator, itself followed by a simple condition:

med eq 42 and next-hop in (10.0.2.2)

A compound condition may also be a simpler expression followed by the or operator and then another

simple condition:

origin is igp or origin is incomplete

An entire compound condition may be enclosed in parentheses:

(med eq 42 and next-hop in (10.0.2.2))

The parentheses may serve to make the grouping of subconditions more readable, or they may force the

evaluation of a subcondition as a unit.

In the following example, the highest-precedence not operator applies only to the destination test, the

and operator combines the result of the not expression with the community test, and the or operator

combines that result with the MED test.

med eq 10 or not destination in (10.1.3.0/24) and community matches-any

([12..34]:[56..78])

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With a set of parentheses to express the precedence, the result is the following:

med eq 10 or ((not destination in (10.1.3.0/24)) and community matches-any

([12..34]:[56..78])

The following is another example of a complex expression:

(origin is igp or origin is incomplete or not med eq 42) and next-hop in (10.0.2.2)

The left conjunction is a compound condition enclosed in parentheses. The first simple condition of the

inner compound condition tests the value of the origin attribute; if it is Interior Gateway Protocol (IGP),

then the inner compound condition is true. Otherwise, the evaluation moves on to test the value of the

origin attribute again, and if it is incomplete, then the inner compound condition is true. Otherwise, the

evaluation moves to check the next component condition, which is a negation of a simple condition.

apply

As discussed in the sections on policy definitions and parameterization of policies, the apply command

executes another policy (either parameterized or unparameterized) from within another policy, which

allows for the reuse of common blocks of policy. When combined with the ability to parameterize

common blocks of policy, the apply command becomes a powerful tool for reducing repetitive

configuration.

Attach Points

Policies do not become useful until they are applied to routes, and for policies to be applied to routes

they need to be made known to routing protocols. In BGP, for example, there are several situations where

policies can be used, the most common of these is defining import and export policy. The policy attach

point is the point in which an association is formed between a specific protocol entity, in this case a BGP

neighbor, and a specific named policy. It is important to note that a verification step happens at this point.

Each time a policy is attached, the given policy and any policies it may apply are checked to ensure that

the policy can be validly used at that attach point. For example, if a user defines a policy that sets the

IS-IS level attribute and then attempts to attach this policy as an inbound BGP policy, the attempt would

be rejected because BGP routes do not carry IS-IS attributes. Likewise, when policies are modified that

are in use, the attempt to modify the policy is verified against all current uses of the policy to ensure that

the modification is compatible with the current uses.

Each protocol has a distinct definition of the set of attributes (commands) that compose a route. For

example, BGP routes may have a community attribute, which is undefined in OSPF. Routes in IS-IS have

a level attribute, which is unknown to BGP. Routes carried internally in the RIB may have a tag attribute.

When a policy is attached to a protocol, the protocol checks the policy to ensure the policy operates using

route attributes known to the protocol. If the protocol uses unknown attributes, then the protocol rejects

the attachment. For example, OSPF rejects attachment of a policy that tests the values of BGP

communities.

The situation is made more complex by the fact that each protocol has access to at least two distinct route

types. In addition to native protocol routes, for example BGP or IS-IS, some protocol policy attach points

operate on RIB routes, which is the common central representation. Using BGP as an example, the

protocol provides an attach point to apply policy to routes redistributed from the RIB to BGP. An attach

point dealing with two different kinds of routes permits a mix of operations: RIB attribute operations for

matching and BGP attribute operations for setting.

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Note The protocol configuration rejects attempts to attach policies that perform unsupported operations.

The following sections describe the protocol attach points, including information on the attributes

(commands) and operations that are valid for each attach point.

•BGP Policy Attach Points, page RC-224

•OSPF Policy Attach Points, page RC-231

•OSPFv3 Policy Attach Points, page RC-232

•IS-IS Policy Attach Points, page RC-234

See the Cisco IOS XR Routing Command Reference for more information on the attributes and

operations.

BGP Policy Attach Points

This section describes each of the BGP policy attach points and provides a summary of the BGP

attributes and operators.

Aggregation

The aggregation attach point generates an aggregate route to be advertised based on the conditional

presence of subcomponents of that aggregate. Policies attached at this attach point are also able to set

any of the valid BGP attributes on the aggregated routes. For example, the policy could set a community

value or a MED on the aggregate that is generated. The specified aggregate is generated if any routes

evaluated by the named policy pass the policy. More specifics of the aggregate are filtered using the

suppress-route keyword. Any actions taken to set attributes in the route affect attributes on the

aggregate.

In the policy language, the configuration is controlled by which routes pass the policy. The suppress map

was used to selectively filter or suppress specific components of the aggregate when the summary-only

flag is not set. In other words, when the aggregate and more specific components are being sent, some

of the more specific components can be filtered using a suppress map. In the policy language, this is

controlled by selecting the route and setting the suppress flag. The attribute-map allowed the user to set

specific attributes on the aggregated route. In the policy language, setting attributes on the aggregated

route is controlled by normal action operations.

In the following example, the aggregate address 10.0.0.0/8 is generated if there are any component routes

in the range 10.0.0.0/8 ge 8 le 25 except for 10.2.0.0/24. Because summary-only is not set, all

components of the aggregate are advertised. However, the specific component 10.1.0.0 are suppressed.

route-policy sample

if destination in (10.0.0.0/8 ge 8 le 25) then

set community (10:33)

endif

if destination in (10.2.0.0/24) then

drop

endif

if destination in (10.1.0.0/24) then

suppress-route

endif

end-policy

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router bgp 2

address-family ipv4

aggregate-address 10.0.0.0/8 policy sample

Dampening

The dampening attach point controls the default route-dampening behavior within BGP. Unless

overridden by a more specific policy on the associate peer, all routes in BGP apply the associated policy

to set their dampening attributes.

The following policy sets dampening values for BGP IPv4 unicast routes. Those routes that are more

specific than a /25 take longer to recover after they have been dampened than routes that are less specific

than /25.

route-policy sample_damp

if destination in (0.0.0.0/0 ge 25) then

set dampening halflife 30 others default

else

set dampening halflife 20 others default

endif

end-policy

router bgp 2

address-family ipv4 unicast

bgp dampening policy sample_damp

Default Originate

The default originate attach point allows the default route (0.0.0.0/0) to be conditionally generated and

advertised to a peer, based on the presence of other routes. It accomplishes this configuration by

evaluating the associated policy against routes in the Routing Information Base (RIB). If any routes pass

the policy, the default route is generated and sent to the relevant peer.

The following policy generates and sends a default-route to the BGP neighbor 10.0.0.1 if any routes that

match 10.0.0.0/8 ge 8 le 32 are present in the RIB.

route-policy sample-originate

if rib-has-route in (10.0.0.0/8 ge 8 le 32) then

pass

endif

end-policy

router bgp 2

neighbor 10.0.0.1

remote-as 3

address-family ipv4 unicast

default-originate policy sample-originate

Note The current implementation of default origination policy permits matching only on destination address.

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Neighbor Export

The neighbor export attach point selects the BGP routes to send to a given peer or group of peers. The

routes are selected by running the set of possible BGP routes through the associated policy. Any routes

that pass the policy are then sent as updates to the peer or group of peers. The routes that are sent may

have had their BGP attributes altered by the policy that has been applied.

The following policy sends all BGP routes to neighbor 10.0.0.5. Routes that are tagged with any

community in the range 2:100 to 2:200 are sent with a MED of 100 and a community of 2:666. The rest

of the routes are sent with a MED of 200 and a community of 2:200.

route-policy sample-export

if community matches-any (2:[100-200]) then

set med 100

set community (2:666)

else

set med 200

set community (2:200)

endif

end-policy

router bgp 2

neighbor 10.0.0.5

remote-as 3

address-family ipv4 unicast

route-policy sample-export out

Neighbor Import

The neighbor import attach point controls the reception of routes from a specific peer. All routes that are

received by a peer are run through the attached policy. Any routes that pass the attached policy are passed

to the BGP Routing Information Base (BRIB) as possible candidates for selection as best path routes.

When a BGP import policy is modified, it is necessary to rerun all the routes that have been received

from that peer against the new policy. The modified policy may now discard routes that were previously

allowed through, allow through previously discarded routes, or change the way the routes are modified.

A new configuration option in BGP (bgp auto-policy-soft-reset) that allows this modification to happen

automatically in cases for which either soft reconfiguration is configured or the BGP route-refresh

capability has been negotiated.

The following example shows how to receive routes from neighbor 10.0.0.1. Any routes received with

the community 3:100 have their local preference set to 100 and their community tag set to 2:666. All

other routes received from this peer have their local preference set to 200 and their community tag set to

2:200.

route-policy sample_import

if community matches-any (3:100) then

set local-preference 100

set community (2:666)

else

set local-preference 200

set community (2:200)

endif

end-policy

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router bgp 2

neighbor 10.0.0.1

remote-as 3

address-family ipv4 unicast

route-policy sample_import in

Network

The network attach point controls the injection of routes from the RIB into BGP. A route policy attached

at this point is able to set any of the valid BGP attributes on the routes that are being injected.

The following example shows a route policy attached at the network attach point that sets the well-known

community no-export for any routes more specific than /24:

route-policy NetworkControl

if destination in (0.0.0.0/0 ge 25) then

set community (no-export) additive

endif

end-policy

router bgp 2

address-family ipv4 unicast

network 172.16.0.5/27 route-policy NetworkControl

Redistribute

The redistribute attach point allows routes from other sources to be advertised by BGP. The policy

attached at this point is able to set any of the valid BGP attributes on the routes that are being

redistributed. Likewise, selection operators allow a user to control what route sources are being

redistributed and which routes from those sources.

The following example shows how to redistribute all routes from OSPF instance 12 into BGP. If OSPF

were carrying a default route, it is dropped. Routes carrying a tag of 10 have their local preference set

to 300 and the community value of 2:666 and no-advertise attached. All other routes have their local

preference set to 200 and a community value of 2:100 set.

route-policy sample_redistribute

if destination in (0.0.0.0/0) then

drop

endif

if tag eq 10 then

set local-preference 300

set community (2:666, no-advertise)

else

set local-preference 200

set community (2:100)

endif

end-policy

router bgp 2

address-family ipv4 unicast

redistribute ospf 12 route-policy sample_redistribute

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Show bgp

The show bgp attach point allows the user to display selected BGP routes that pass the given policy. Any

routes that are not dropped by the attached policy are displayed in a manner similar to the output of the

show ip bgp command.

In the following example, the show bgp route-policy command is used to display any BGP routes

carrying a MED of 5:

route-policy sample-display

if med eq 5 then

pass

endif

end-policy

show bgp route-policy sample-display

A show bgp policy route-policy command also exists, which runs all routes in the RIB past the named

policy as if the RIB were an outbound BGP policy. This command then displays what each route looked

like before it was modified and after it was modified, as shown in the following example:

RP/0/RP0/CPU0:router# show rpl route-policy test2

route-policy test2

if (destination in (10.0.0.0/8 ge 8 le 32)) then

set med 333

endif

end-policy

RP/0/RP0/CPU0:router# show bgp

BGP router identifier 10.0.0.1, local AS number 2

BGP main routing table version 11

BGP scan interval 60 secs

Status codes:s suppressed, d damped, h history, * valid, > best

i - internal, S stale

Origin codes:i - IGP, e - EGP, ? - incomplete

Network Next Hop Metric LocPrf Weight Path

*> 10.0.0.0 10.0.1.2 10 0 3 ?

*> 10.0.0.0/9 10.0.1.2 10 0 3 ?

*> 10.0.0.0/10 10.0.1.2 10 0 3 ?

*> 10.0.0.0/11 10.0.1.2 10 0 3 ?

*> 10.1.0.0/16 10.0.1.2 10 0 3 ?

*> 10.3.30.0/24 10.0.1.2 10 0 3 ?

*> 10.3.30.128/25 10.0.1.2 10 0 3 ?

*> 10.128.0.0/9 10.0.1.2 10 0 3 ?

*> 10.255.0.0/24 10.0.101.2 1000 555 0 100 e

*> 10.255.64.0/24 10.0.101.2 1000 555 0 100 e

....

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RP/0/RP0/CPU0:router# show bgp policy route-policy test2

10.0.0.0/8 is advertised to 10.0.101.2

Path info:

neighbor:10.0.1.2 neighbor router id:10.0.1.2

valid external best

Attributes after inbound policy was applied:

next hop:10.0.1.2

MET ORG AS

origin:incomplete neighbor as:3 metric:10

aspath:3

Attributes after outbound policy was applied:

next hop:10.0.1.2

MET ORG AS

origin:incomplete neighbor as:3 metric:333

aspath:2 3

...

Table Policy

The table policy attach point allows the user to configure traffic-index values on routes as they are

installed into the global routing table. This attach point supports the BGP policy accounting feature.

BGP policy accounting uses the traffic indexes that are set on the BGP routes to track various counters.

This way, router operators can select different sets of BGP route attributes using the matching operations

and then set different traffic indexes for each different class of route they are interested in tracking.

The following example shows how to set the traffic index to 10 in IPv4 unicast routes that originated

from autonomous system 10. Likewise, any IPv4 unicast routes that originated from autonomous system

11 have their traffic index set to 11 when they are installed into the FIB. These traffic indexes are then

used to count traffic being forwarded on these routes in line cards by enabling the BGP policy accounting

counters on the interfaces of interest.

route-policy sample-table

if as-path originates-from ‘10’ then

set traffic-index 10

elseif as-path originates-from ‘11’ then

set traffic-index 11

endif

end-policy

router bgp 2

address-family ipv4 unicast

table-policy sample-table

BGP Attributes and Operators

Table 3 summarizes the BGP attributes and operators.

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Some BGP route attributes are inaccessible from some BGP attach points for various reasons. For

example, the set med igp-cost only command makes sense when there is a configured igp-cost to

provide a source value. Table 4 summarizes which operations are valid and where they are valid.

Table 3 BGP Attributes and Operators

Attribute Match Set

as-path in

is-local

length

neighbor-is

originates-from

passes-though

unique-length

prepend

community is-empty

matches-any

matches-every

delete

set

dampening n/a set dampening... to set

values that control the

dampening (see

Dampening, page RC-225)

destination in n/a

extended community is-empty

matches-any

matches-every

delete

set

local-preference n/a set

med is, eq, ge, le set

set +

set -

next-hop in set

origin is set

rib-has-route in n/a

route-type is n/a

source in n/a

suppress-route n/a suppress-route

tag is, eq, ge, le set

traffic-index n/a set

unsuppress-route n/a unsuppress-route

weight n/a set

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OSPF Policy Attach Points

This section describes each of the OSPF policy attach points and provides a summary of the OSPF

attributes and operators.

Default Originate

The default originate attach point allows the user to conditionally inject the default route 0.0.0.0/0 into

the OSPF link-state database, which is done by evaluating the attached policy. If any routes in the local

RIB pass the policy, then the default route is inserted into the link-state database.

The following example shows how to generate a default route if any of the routes that match 10.0.0.0/8

ge 8 le 25 are present in the RIB:

route-policy ospf-originate

if rib-has-route in (10.0.0.0/8 ge 8 le 25) then

pass

endif

end-policy

router ospf 1

default-information originate policy ospf-originate

Redistribute

The redistribute attach point within OSPF injects routes from other routing protocol sources into the

OSPF link-state database, which is done by selecting the route types it wants to import from each

protocol. It then sets the OSPF parameters of cost and metric type. The policy can control how the routes

are injected into OSPF by using the set level command.

The following example shows how to redistribute routes from IS-IS instance instance_10 into OSPF

instance 1 using the policy OSPF-redist. The policy sets the metric type to type-2 for all redistributed

routes. IS-IS routes with a tag of 10 have their cost set to 100, and IS-IS routes with a tag of 20 have

their OSPF cost set to 200. Any IS-IS routes not carrying a tag of either 10 or 20 are not be redistributed

into the OSPF link-state database.

Table 4 Restricted BGP Operations by Attach Point

import export aggregation redistribution

prepend as-path eBGP only eBGP only n/a n/a

set med igp-cost forbidden eBGP only forbidden forbidden

set weight n/a forbidden n/a n/a

suppress forbidden forbidden n/a forbidden

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route-policy OSPF-redist

set metric-type type-2

if tag eq 10 then

set cost 100

elseif tag eq 20 then

set cost 200

else

drop

endif

end-policy

router ospf 1

redistribute isis instance_10 policy OSPF-redist

OSPF Attributes and Operators

Table 5 summarizes the OSPF attributes and operators.

OSPFv3 Policy Attach Points

This section describes each of the OSPFv3 policy attach points and provides a summary of the BGP

attributes and operators.

Default Originate

The default originate attach point allows the user to conditionally inject the default route 0::/0 into the

OSPFv3 link-state database, which is done by evaluating the attached policy. If any routes in the local

RIB pass the policy, then the default route is inserted into the link-state database.

The following example shows how to generate a default route if any of the routes that match 2001::/96

are present in the RIB:

route-policy ospfv3-originate

if rib-has-route in (2001::/96) then

pass

endif

end-policy

Table 5 OSPF Attributes and Operators

Attribute Match Set

cost n/a set

destination in n/a

metric-type n/a set

rib-has-route in n/a

route-type is n/a

tag eq, ge, le set

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router ospfv3 1

default-information originate policy ospfv3-originate

Redistribute

The redistribute attach point within OSPFv3 injects routes from other routing protocol sources into the

OSPFv3 link-state database, which is done by selecting the route types it wants to import from each

protocol. It then sets the OSPFv3 parameters of cost and metric type. The policy can control how the

routes are injected into OSPFv3 by using the metric type command.

The following example shows how to redistribute routes from BGP instance instance_15 into OSPF

instance 1 using the policy OSPFv3-redist. The policy sets the metric type to type-2 for all redistributed

routes. BGP routes with a tag of 10 have their cost set to 100, and BGP routes with a tag of 20 have their

OSPFv3 cost set to 200. Any BGP routes not carrying a tag of either 10 or 20 are not be redistributed

into the OSPFv3 link-state database.

route-policy OSPFv3-redist

set metric-type type-2

if tag eq 10 then

set cost 100

elseif tag eq 20 then

set cost 200

else

drop

endif

end-policy

router ospfv3 1

redistribute bgp instance_15 policy OSPFv3-redist

OSPFv3 Attributes and Operators

Table 6 summarizes the OSPFv3 attributes and operators.

Table 6 OSPFv3 Attributes and Operators

Attribute Match Set

cost n/a set

destination in n/a

metric-type n/a set

rib-has-route in n/a

route-type is n/a

tag eq, ge, le set

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IS-IS Policy Attach Points

This section describes each of the IS-IS policy attach points and provides a summary of the BGP

attributes and operators.

Redistribute

The redistribute attach point within IS-IS allows routes from other protocols to be readvertised by IS-IS.

The policy is a set of control structures for selecting the types of routes that a user wants to redistribute

into IS-IS. The policy can also control which IS-IS level the routes are injected into and at what metric

values.

The following example shows how to redistribute routes from IS-IS instance 1 into IS-IS instance

instance_10 using the policy ISIS-redist. This policy sets the level to level-1-2 for all redistributed

routes. OSPF routes with a tag of 10 have their metric set to 100, and IS-IS routes with a tag of 20 have

their IS-IS metric set to 200. Any IS-IS routes not carrying a tag of either 10 or 20 are not be redistributed

into the IS-IS database.

route-policy ISIS-redist

set level level-1-2

if tag eq 10 then

set metric 100

elseif tag eq 20 then

set metric 200

else

drop

endif

end-policy

router isis instance_10

address-family ipv4 unicast

redistribute ospf 1 policy ISIS-redist

IS-IS Attributes and Operators

Table 7 summarizes the IS-IS attributes and operators.

Table 7 IS-IS Attributes and Operators

Attribute Match Set

Destination in n/a

Level n/a set

metric n/a set

metric-type n/a set

rib-has-route in n/a

route-type is n/a

tag eq, ge, le n/a

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Attached Policy Modification

Policies that are in use do, on occasion, need to be modified. In the traditional configuration model, a

policy modification would be done by completely removing the policy and re-entering it. However, this

model allows for a window of time in which no policy is attached and default actions to be used, which

is an opportunity for inconsistencies to exist. To close this window of opportunity, you can modify a

policy in use at an attach point by respecifying it, which allows for policies that are in use to be changed,

without having a window of time in which no policy is applied at the given attach point.

Note A route policy or set that is in use at an attach point cannot be removed because this removal would result

in an undefined reference. An attempt to remove a route policy or set that is in use at an attach point

results in an error message to the user.

Nonattached Policy Modification

As long as a given policy is not attached at an attach point, the policy is allowed to refer to nonexistent

sets and policies. Configurations can be built that reference sets or policy blocks that are not yet defined,

and then later those undefined policies and sets can be filled in. This method of building configurations

gives much greater flexibility in policy definition. Every piece of policy you want to reference while

defining a policy need not exist in the configuration. Thus, you can define a policy sample1 that

references a policy sample2 using an apply statement even if the policy sample2 does not exist. Similarly,

you can enter a policy statement that refers to a nonexistent set.

However, the existence of all referenced policies and sets is enforced when a policy is attached. Thus, if

a user attempts to attach the policy sample1 with the reference to an undefined policy sample2 at an

inbound BGP policy using the statement neighbor 1.2.3.4 address-family ipv4 unicast policy sample1

in, the configuration attempt is rejected because the policy sample2 does not exist.

Editing Routing Policy Configuration Elements

RPL is based on statements rather than on lines. That is, within the begin-end pair that brackets policy

statements from the CLI, a new line is merely a separator, the same as a space character.

The CLI provides the means to enter and delete route policy statements. RPL provides a means to edit

the contents of the policy between the begin-end brackets using a microemacs editor.

Editing Routing Policy Configuration Elements Using the EMACS Editor

To edit the contents of a routing policy, use the following CLI command in EXEC mode:

edit {route-policy | prefix-set | as-path-set | community-set | extended-community-set}

name

A copy of the route policy is copied to a temporary file and the editor is launched. After editing, save

the changes by using the save-buffer command, C-X C-S (Control-X Control-S). To exit the editor, use

the quit command, Control-X Control-C. When you quit the editor, the buffer is committed. If there are

no parse errors, the configuration is committed:

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RP/0/RP0/CPU0:router# edit route-policy policy_A

----------------------------------------

== MicroEMACS 3.8b () == rpl_edit.139281 ==

if destination in (2001::/8) then

drop

endif

end-policy

== MicroEMACS 3.8b () == rpl_edit.139281 ==

Parsing.

83 bytes parsed in 1 sec (82)bytes/sec

Committing.

1 items committed in 1 sec (0)items/sec

Updating.

Updated Commit database in 1 sec

RP/0/RP0/CPU0:router#

If there are parse errors, you are asked whether editing should continue:

RP/0/RP0/CPU0:router#edit route-policy policy_B

== MicroEMACS 3.8b () == rpl_edit.141738

route-policy policy_B

set metric-type type_1

if destination in (2001::/8) then

drop

endif

end-policy

== MicroEMACS 3.8b () == rpl_edit.141738 ==

Parsing.

105 bytes parsed in 1 sec (103)bytes/sec

% Syntax/Authorization errors in one or more commands.!! CONFIGURATION

FAILED DUE TO SYNTAX/AUTHORIZATION ERRORS

set metric-type type_1

if destination in (2001::/8) then

drop

endif

end-policy

Continue editing? [no]:

If you answer yes, the editor continues on the text buffer from where you left off. If you answer no, the

running configuration is not changed and the editing session is ended.

Editing Routing Policy Configuration Elements Using the CLI

The CLI allows you to enter and delete route policy statements. You can complete a policy configuration

block by entering applicable commands such as end-policy or end-set. Alternatively, the CLI interpreter

allows you to use the exit command to complete a policy configuration block. The abort command is

used to discard the current policy configuration and return to global configuration mode.

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How to Implement Routing Policy

This section contains the following procedures:

•Defining a Route Policy, page RC-237 (required)

•Attaching a Routing Policy to a BGP Neighbor, page RC-238 (required)

•Modifying a Routing Policy Using the Microemacs Editor, page RC-240 (optional)

Defining a Route Policy

This task explains how to define a route policy.

Note If you want to modify an existing routing policy using the command-line interface (CLI), you must

redefine the policy by completing this task.

SUMMARY STEPS

1. configure

2. route-policy name

3. end-policy

4. end

commit

DETAILED STEPS

Command or Action Purpose

Step 1 configure

Example:

RP/0/RP0/CPU0:router# configure

Enters global configuration mode.

Step 2 route-policy

name

Example:

RP/0/RP0/CPU0:router(config)# route-policy

sample1

Enters route-policy configuration mode.

•After the route-policy has been entered, a group of

commands can be entered to define the route-policy.

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Attaching a Routing Policy to a BGP Neighbor

This task explains how to attach a routing policy to a BGP neighbor. The procedure to attach a routing

policy to an IS-IS or OSPF neighbor is the same as BGP, except that the commands and applicable

arguments vary.

Prerequisites

A routing policy must be preconfigured and well defined prior to it being applied at an attach point. If a

policy is not predefined, an error message is generated stating that the policy is not defined.

SUMMARY STEPS

1. configure

2. router bgp as-number

3. neighbor ip-address

4. address-family {ipv4 | ipv6} {multicast | unicast}

5. route-policy route-policy-name {in | out}

6. end

commit

Step 3 end-policy

Example:

RP/0/RP0/CPU0:router(config-rpl)# end-policy

Ends the definition of a route policy and exits route-policy

configuration mode.

Step 4 end

commit

Example:

RP/0/RP0/CPU0:router(config)# end

RP/0/RP0/CPU0:router(config)# commit

Saves configuration changes.

•When you issue the end command, the system prompts

you to commit changes:

Uncommitted changes found, commit them before

exiting(yes/no/cancel)?

[cancel]:

–

Entering yes saves configuration changes to the

running configuration file, exits the configuration

session, and returns the router to EXEC mode.

–

Entering no exits the configuration session and

returns the router to EXEC mode without

committing the configuration changes.

–

Entering cancel leaves the router in the current

configuration session without exiting or

committing the configuration changes.

Use the commit command to save the configuration

changes to the running configuration file and remain within

the configuration session.

Command or Action Purpose

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DETAILED STEPS

Command or Action Purpose

Step 1 configure

Example:

RP/0/RP0/CPU0:router# configure

Enters global configuration mode.

Step 2 router bgp

as-number

Example:

RP/0/RP0/CPU0:router(config)# router bgp 125

Configures a BGP routing process and enters router

configuration mode.

•The as-number argument identifies the

autonomous system in which the router resides.

Valid values are from 0 to 65535. Private

autonomous system numbers that can be used in

internal networks range from 64512 to 65535.

Step 3 neighbor

ip-address

Example:

RP/0/RP0/CPU0:router(config-bgp)# neighbor

10.0.0.20

Specifies a neighbor IP address.

Step 4 address-family {ipv4 | ipv6} {multicast | unicast}

Example:

RP/0/RP0/CPU0:router(config-bgp-nbr)#

address-family ipv4 unicast

Specifies the address family, the version of IP that is

in use, and either multicast or unicast.

•Enters address family configuration mode.

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Modifying a Routing Policy Using the Microemacs Editor

This task explains how to modify an existing routing policy using the microemacs editor.

SUMMARY STEPS

1. edit {route-policy | prefix-set | as-path-set | community-set | extended-community-set} name

2. show rpl route-policy name [detail]

3. show rpl prefix-set name

Step 5 route-policy

policy-name

{in | out}

Example:

RP/0/RP0/CPU0:router(config-bgp-nbr-af)#

route-policy example1 in

Attaches the route-policy, which must be well formed

and predefined.

Step 6 end

commit

Example:

RP/0/RP0/CPU0:router(config-bgp-nbr-af)# end

RP/0/RP0/CPU0:router(config-bgp-nbr-af)# commit

Saves configuration changes.

•When you issue the end command, the system

prompts you to commit changes:

Uncommitted changes found, commit them

before exiting(yes/no/cancel)?

[cancel]:

–

Entering yes saves configuration changes to

the running configuration file, exits the

configuration session, and returns the router

to EXEC mode.

–

Entering no exits the configuration session

and returns the router to EXEC mode without

committing the configuration changes.

–

Entering cancel leaves the router in the

current configuration session without exiting

or committing the configuration changes.

Use the commit command to save the configuration

changes to the running configuration file and remain

within the configuration session.

Command or Action Purpose

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DETAILED STEPS

Configuration Examples for Implementing Routing Policy

This section provides the following configuration examples:

•Routing Policy Definition: Example, page RC-241

•Simple Inbound Policy: Example, page RC-242

•Modular Inbound Policy: Example, page RC-243

•Translating Cisco IOS Route Maps to Cisco IOS XR Routing Policy Language: Example,

page RC-244

Routing Policy Definition: Example

In the following example, a BGP route policy named sample1 is defined using the route-policy name

command. The policy compares the network layer reachability information (NLRI) to the elements in

the prefix set test. If it evaluates to true, the policy performs the operations in the then clause. If it

evaluates to false, the policy performs the operations in the else clause, that is, sets the MED value to

200 and adds the community 2:100 to the route. The final steps of the example commit the configuration

to the router, exit configuration mode, and display the contents of route policy sample1.

Command or Action Purpose

Step 1 edit {route-policy | prefix-set | as-path-set |

community-set | extended-community-set}

name

Example:

RP/0/RP0/CPU0:router# edit route-policy sample1

Identifies the route policy, prefix set, AS path set,

community set, or extended community set name to be

modified.

•A copy of the route policy, prefix set, AS path set,

community set, or extended community set is copied to

a temporary file and the microemacs editor is launched.

When you finish editing the policy or set, save the

changes by using the save-buffer command, ^X^S

(Control-X Control-S).

To commit the changed configuration:

•save the buffer (Control-X Control-S)

•exit MicroEmacs (Control-X Control-C)

Step 2 show rpl route-policy

name

[detail]

Example:

RP/0/RP0/CPU0:router# show rpl route-policy

sample2

(Optional) Displays the configuration of a specific named

route policy.

•Use the detail keyword to display all policies and sets

that a policy uses.

Step 3 show rpl prefix-set

name

Example:

RP/0/RP0/CPU0:router# show rpl prefix-set

prefixset1

(Optional) Displays the contents of a named prefix set.

•To display the contents of a named AS path set,

community set, or extended community set, replace the

prefix-set keyword with as-path-set, community-set,

or extcommunity-set, respectively.

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configure

route-policy sample1

if destination in test then

drop

else

set med 200

set community (2:100) additive

endif

end-policy

end

show config running route-policy sample1

Building configuration...

route-policy sample1

if destination in test then

drop

else

set med 200

set community (2:100) additive

endif

end-policy

Simple Inbound Policy: Example

The following policy discards any route whose network layer reachability information (NLRI) specifies

a prefix longer than /24, and any route whose NLRI specifies a destination in the address space reserved

by RFC 1918. For all remaining routes, it sets the MED and local preference, and adds a community to

the list in the route.

For routes whose community lists include any values in the range from 101:202 to 106:202 that have a

16-bit tag portion containing the value 202, the policy prepends autonomous system number 2 twice, and

adds the community 2:666 to the list in the route. Of these routes, if the MED is either 666 or 225, then

the policy sets the origin of the route to incomplete, and otherwise sets the origin to IGP.

For routes whose community lists do not include any of the values in the range from 101:202 to 106:202,

the policy adds the community 2:999 to the list in the route.

prefix-set too-specific

0.0.0.0/0 ge 25 le 32

end-set

prefix-set rfc1918

10.0.0.0/8 le 32,

172.16.0.0/12 le 32,

192.168.0.0/16 le 32

end-set

route-policy inbound-tx

if destination in too-specific or destination in rfc1918 then

drop

endif

set med 1000

set local-preference 90

set community (2:1001) additive

if community matches-any ([101..106]:202) then

prepend as-path 2 2

set community (2:666) additive

if med is 666 or med is 225 then

set origin incomplete

else

set origin igp

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Cisco IOS XR Routing Configuration Guide

endif

else

set community (2:999) additive

endif

end-policy

router bgp 2

neighbor 10.0.1.2 address-family ipv4 unicast route-policy inbound-tx in

Modular Inbound Policy: Example

The following policy example shows how to build two inbound policies, in-100 and in-101, for two

different peers. In building the specific policies for those peers, the policy reuses some common blocks

of policy that may be common to multiple peers. It builds a few basic building blocks, the policies

common-inbound, filter-bogons, and set-lpref-prepend.

The filter-bogons building block is a simple policy that filters all undesirable routes, such as those from

the RFC 1918 address space. The policy set-lpref-prepend is a utility policy that can set the local

preference and prepend the AS path according to parameterized values that are passed in. The

common-inbound policy uses these filter-bogons building blocks to build a common block of inbound

policy. The common-inbound policy is used as a building block in the construction of in-100 and in-101

along with the set-lpref-prepend building block.

This is a simple example that illustrates the modular capabilities of the policy language.

prefix-set bogon

10.0.0.0/8 ge 8 le 32,

0.0.0.0,

0.0.0.0/0 ge 27 le 32,

192.168.0.0/16 ge 16 le 32

end-set

route-policy in-100

apply common-inbound

if community matches-any ([100..120]:135) then

apply set-lpref-prepend (100,100,2)

set community (2:1234) additive

else

set local-preference 110

endif

if community matches-any ([100..666]:[100..999]) then

set med 444

set local-preference 200

set community (no-export) additive

endif

end-policy

route-policy in-101

apply common-inbound

if community matches-any ([101..200]:201) then

apply set-lpref-prepend(100,101,2)

set community (2:1234) additive

else

set local-preference 125

endif

end-policy

route-policy filter-bogons

if destination in bogon then

drop

else

Implementing Routing Policy on Cisco IOS XR Software

Additional References

RC-244

Cisco IOS XR Routing Configuration Guide

pass

endif

end-policy

route-policy common-inbound

apply filter-bogons

set origin igp

set community (2:333)

end-policy

route-policy set-lpref-prepend($lpref,$as,$prependcnt)

set local-preference $lpref

prepend as-path $as $prependcnt

end-policy

Translating Cisco IOS Route Maps to Cisco IOS XR Routing Policy Language:

Example

RPL performs the same functions as route-maps. See the Converting Cisco IOS Configurations to

Cisco IOS XR Configurations guide.

Additional References

The following sections provide references related to implementing RPL.

Related Documents

Standards

Related Topic Document Title

Routing policy language commands: complete

command syntax, command modes, command history,

defaults, usage guidelines, and examples

Routing Policy Language Commands on Cisco IOS XR Software,

Release 3.2

Regular expression syntax “Understanding Regular Expressions, Special Characters and

Patterns” appendix in the Cisco IOS XR Getting Started Guide

Standards Title

Draft-ietf-idr-bgp4-26.txt A Border Gateway Protocol 4, by Y. Rekhter, T.Li, S. Hares

Implementing Routing Policy on Cisco IOS XR Software

Additional References

RC-245

Cisco IOS XR Routing Configuration Guide

MIBs

RFCs

Technical Assistance

MIBs MIBs Link

There are no applicable MIBs for this module. To locate and download MIBs for selected platforms using

Cisco IOS XR software, use the Cisco MIB Locator found at the

following URL:

http://cisco.com/public/sw-center/netmgmt/cmtk/mibs.shtml

RFCs Title

No new or modified RFCs are supported by this

feature, and support for existing RFCs has not been

modified by this feature.

—

Description Link

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including links to products, technologies, solutions,

technical tips, and tools. Registered Cisco.com users

can log in from this page to access even more content.

http://www.cisco.com/techsupport

Implementing Routing Policy on Cisco IOS XR Software

Additional References

RC-246

Cisco IOS XR Routing Configuration Guide

RC-247

Cisco IOS XR Routing Configuration Guide

Implementing Static Routes on Cisco IOS XR

Software

Static routes are user-defined routes that cause packets moving between a source and a destination to

take a specified path. Static routes can be important if the Cisco IOS XR software cannot build a route

to a particular destination. They are useful for specifying a gateway of last resort to which all unroutable

packets are sent.

This module describes the tasks you need to implement static routes on your Cisco IOS XR network.

Note For more information about static routes on the Cisco IOS XR software and complete descriptions of the

static routes commands listed in this module, see the “Related Documents” section of this module. To

locate documentation for other commands that might appear while executing a configuration task, search

online in the Cisco IOS XR software master command index.

Feature History for Implementing Static Routes on Cisco IOS XR Software

Contents

•Prerequisites for Implementing Static Routes on Cisco IOS XR Software, page RC-248

•Information About Implementing Static Routes on Cisco IOS XR Software, page RC-248

•How to Implement Static Routes on Cisco IOS XR Software, page RC-250

•Configuration Examples, page RC-255

•Where to Go Next, page RC-255

•Additional References, page RC-256

Release Modification

Release 2.0 This feature was introduced on the Cisco CRS-1.

Release 3.0 No modification.

Release 3.2 Support was added for the Cisco XR 12000 Series Router.

Implementing Static Routes on Cisco IOS XR Software

Prerequisites for Implementing Static Routes on Cisco IOS XR Software

RC-248

Cisco IOS XR Routing Configuration Guide

Prerequisites for Implementing Static Routes on Cisco IOS XR

Software

To use this command, you must be in a user group associated with a task group that includes the proper

task IDs. For detailed information about user groups and task IDs, see the Configuring AAA Services on

Cisco IOS XR Software module of the Cisco IOS XR System Security Configuration Guide.

Information About Implementing Static Routes on Cisco IOS XR

Software

To implement static routes you need to understand the following concepts:

•Static Route Functional Overview, page RC-248

•Default Administrative Distance, page RC-248

•Directly Connected Routes, page RC-249

Static Route Functional Overview

Static routes are entirely user configurable and can point to a next-hop interface, next-hop IP address, or

both. In Cisco IOS XR software, if an interface was specified, then the static route is installed in the

Routing Information Base (RIB) if the interface is reachable. If an interface was not specified, the route

is installed if the next-hop address is reachable. The only exception to this configuration is when a static

route is configured with the permanent attribute, in which case it is installed in RIB regardless of

reachability.

Networking devices forward packets using route information that is either manually configured or

dynamically learned using a routing protocol. Static routes are manually configured and define an

explicit path between two networking devices. Unlike a dynamic routing protocol, static routes are not

automatically updated and must be manually reconfigured if the network topology changes. The benefits

of using static routes include security and resource efficiency. Static routes use less bandwidth than

dynamic routing protocols, and no CPU cycles are used to calculate and communicate routes. The main

disadvantage to using static routes is the lack of automatic reconfiguration if the network topology

changes.

Static routes can be redistributed into dynamic routing protocols, but routes generated by dynamic

routing protocols cannot be redistributed into the static routing table. No algorithm exists to prevent the

configuration of routing loops that use static routes.

Static routes are useful for smaller networks with only one path to an outside network and to provide

security for a larger network for certain types of traffic or links to other networks that need more control.

In general, most networks use dynamic routing protocols to communicate between networking devices

but may have one or two static routes configured for special cases.

Default Administrative Distance

Static routes have a default administrative distance of 1. A low number indicates a preferred route. By

default, static routes are preferred to routes learned by routing protocols. Therefore, you can configure

an administrative distance with a static route if you want the static route to be overridden by dynamic

Implementing Static Routes on Cisco IOS XR Software

Information About Implementing Static Routes on Cisco IOS XR Software

RC-249

Cisco IOS XR Routing Configuration Guide

routes. For example, you could have routes installed by the Open Shortest Path First (OSPF) protocol

with an administrative distance of 120. To have a static route that would be overridden by an OSPF

dynamic route, specify an administrative distance greater than 120.

Directly Connected Routes

The routing table considers the static routes that point to an interface as “directly connected.” Directly

connected networks are advertised by IGP routing protocols if a corresponding interface command is

contained under the router configuration stanza of that protocol.

In directly attached static routes, only the output interface is specified. The destination is assumed to be

directly attached to this interface, so the packet destination is used as the next hop address. The following

example shows how to specify that all destinations with address prefix 2001:0DB8::/32 are directly

reachable through interface GigabitEthernet 0/5/0/0:

RP/0/RP0/CPU0:router(config)# route ipv6 unicast 2001:0DB8::/32 gigabitethernet 0/5/0/0

Directly attached static routes are candidates for insertion in the routing table only if they refer to a valid

interface; that is, an interface that is both up and has IPv4 or IPv6 enabled on it.

Recursive Static Routes

In a recursive static route, only the next hop is specified. The output interface is derived from the next

hop. The following example shows how to specify that all destinations with address prefix

2001:0DB8::/32 are reachable through the host with address 2001:0DB8:3000::1:

RP/0/RP0/CPU0:router(config)# route ipv6 unicast 2001:0DB8::/32 2001:0DB8:3000::1

A recursive static route is valid (that is, it is a candidate for insertion in the routing table) only when the

specified next hop resolves, either directly or indirectly, to a valid output interface, provided the route

does not self-recurse, and the recursion depth does not exceed the maximum IPv6 forwarding recursion

depth.

A route self-recurses if it is itself used to resolve its own next hop. If a static route becomes

self-recursive, RIB sends a notification to static routes to withdraw the recursive route.

The following example shows how to define a recursive IPv6 static route:

RP/0/RP0/CPU0:router(config)# route ipv6 unicast 2001:0DB8::/32 2001:0DB8:3000::1

This static route is not inserted into the IPv6 routing table because it is self-recursive. The next hop of

the static route, 2001:0DB8:3000:1, resolves through the BGP route 2001:0DB8:3000:0/16, which is

itself a recursive route (that is, it only specifies a next hop). The next hop of the BGP route,

2001:0DB8::0104, resolves through the static route. Therefore, the static route would be used to resolve

its own next hop.

It is not normally useful to manually configure a self-recursive static route, although it is not prohibited.

However, a recursive static route that has been inserted in the routing table may become self-recursive

as a result of some transient change in the network learned through a dynamic routing protocol. If this

occurs, the fact that the static route has become self-recursive will be detected and it will be removed

from the routing table, although not from the configuration. A subsequent network change may cause

the static route to no longer be self-recursive, in which case it will be re-inserted in the routing table.

Implementing Static Routes on Cisco IOS XR Software

How to Implement Static Routes on Cisco IOS XR Software

RC-250

Cisco IOS XR Routing Configuration Guide

Fully Specified Static Routes

In a fully specified static route, both the output interface and next hop are specified. This form of static

route is used when the output interface is a multiaccess one and it is necessary to explicitly identify the

next hop. The next hop must be directly attached to the specified output interface. The following

example shows a definition of a fully specified static route:

RP/0/RP0/CPU0:router(config)# route ipv6 unicast 2001:0DB8::/32 2001:0DB8:3000::1

A fully specified route is valid (that is, a candidate for insertion into the routing table) when the specified

interface is IPv4 or IPv6 enabled and up.

Floating Static Routes

Floating static routes are static routes that are used to back up dynamic routes learned through configured

routing protocols. A floating static route is configured with a higher administrative distance than the

dynamic routing protocol it is backing up. As a result, the dynamic route learned through the routing

protocol is always preferred to the floating static route. If the dynamic route learned through the routing

protocol is lost, the floating static route is used in its place. The following example shows how to define

a floating static route:

RP/0/RP0/CPU0:router(config)# route ipv6 unicast 2001:0DB8::/32 2001:0DB8:3000::1 210

Any of the three types of static routes can be used as a floating static route. A floating static route must

be configured with an administrative distance that is greater than the administrative distance of the

dynamic routing protocol because routes with smaller administrative distances are preferred.

Note By default, static routes have smaller administrative distances than dynamic routes, so static routes

preferred to dynamic routes.

How to Implement Static Routes on Cisco IOS XR Software

This section contains the following procedures:

•Configuring a Static Route, page RC-250 (required)

•Configuring a Floating Static Route, page RC-251 (optional)

•Changing the Maximum Number of Allowable Static Routes, page RC-253 (optional)

Configuring a Static Route

This task explains how to configure a static route.

SUMMARY STEPS

1. configure

2. route {ipv4 | ipv6} {unicast | multicast} prefix mask {ip-address | interface-type

interface-instance} [distance] [tag tag] [permanent]

Implementing Static Routes on Cisco IOS XR Software

How to Implement Static Routes on Cisco IOS XR Software

RC-251

Cisco IOS XR Routing Configuration Guide

3. end

commit

DETAILED STEPS

Configuring a Floating Static Route

This task explains how to configure a floating static route.

SUMMARY STEPS

1. configure

2. route {ipv4 | ipv6} {unicast | multicast} prefix mask {ip-address | interface-type

interface-instance} [distance] [tag tag] [permanent]

Command or Action Purpose

Step 1 configure

Example:

RP/0/RP0/CPU0:router# configure

Enters global configuration mode.

Step 2 route {ipv4 | ipv6} {unicast | multicast}

prefix mask

{

ip-address

interface-type

interface-instance

} [

distance

] [tag

tag

]

[permanent]

Example:

RP/0/RP0/CPU0:router(config)# route ipv4

unicast 10.0.0.0/8 172.20.16.6 110

Configures an administrative distance of 110.

•This example shows how to route packets for network

10.0.0.0 through to a router at 172.20.16.6 if dynamic

information with administrative distance less than 110

is not available.

Step 3 end

commit

Example:

RP/0/RP0/CPU0:router(config)# end

RP/0/RP0/CPU0:router(config)# commit

Saves configuration changes.

•When you issue the end command, the system prompts

you to commit changes:

Uncommitted changes found, commit them before

exiting(yes/no/cancel)?

[cancel]:

–

Entering yes saves configuration changes to the

running configuration file, exits the configuration

session, and returns the router to EXEC mode.

–

Entering no exits the configuration session and

returns the router to EXEC mode without

committing the configuration changes.

–

Entering cancel leaves the router in the current

configuration session without exiting or

committing the configuration changes.

•Use the commit command to save the configuration

changes to the running configuration file and remain

within the configuration session.

Implementing Static Routes on Cisco IOS XR Software

How to Implement Static Routes on Cisco IOS XR Software

RC-252

Cisco IOS XR Routing Configuration Guide

3. end

commit

DETAILED STEPS

Command or Action Purpose

Step 1 configure

Example:

RP/0/RP0/CPU0:router# configure

Enters global configuration mode.

Step 2 route {ipv4 | ipv6} {unicast | multicast}

prefix mask

{

ip-address

interface-type

interface-instance

} [

distance

] [tag

tag

]

[permanent]

Example:

RP/0/RP0/CPU0:router(config)# route ipv6

unicast 2001:0DB8::/32 2001:0DB8:3000::1 201

In this example, a floating static IPv6 route is being

configured. An administrative distance of 201 is configured

Default administrative distances are as follows:

•Connected interface—0

•Static route—1

Step 3 end

commit

Example:

RP/0/RP0/CPU0:router(config)# end

RP/0/RP0/CPU0:router(config)# commit

Saves configuration changes.

•When you issue the end command, the system prompts

you to commit changes:

Uncommitted changes found, commit them before

exiting(yes/no/cancel)?

[cancel]:

–

Entering yes saves configuration changes to the

running configuration file, exits the configuration

session, and returns the router to EXEC mode.

–

Entering no exits the configuration session and

returns the router to EXEC mode without

committing the configuration changes.

–

Entering cancel leaves the router in the current

configuration session without exiting or

committing the configuration changes.

•Use the commit command to save the configuration

changes to the running configuration file and remain

within the configuration session.

Implementing Static Routes on Cisco IOS XR Software

How to Implement Static Routes on Cisco IOS XR Software

RC-253

Cisco IOS XR Routing Configuration Guide

Changing the Maximum Number of Allowable Static Routes

This task explains how to change the maximum number of allowable static routes.

Restrictions

The number of static routes that can be configured on a router for a given address family is limited by

default to 4000. The limit can be raised or lowered using the route maximum command. Note that if

you use the route maximum command to reduce the configured maximum allowed number of static

routes for a given address family below the number of static routes currently configured, the change is

rejected. In addition, understand the following behavior: If you commit a batch of routes that would,

when grouped, push the number of static routes configured above the maximum allowed, the first n

routes in the batch are accepted. The number previously configured is accepted, and the remainder are

rejected. The n argument is the difference between the maximum number allowed and number previously

configured.

SUMMARY STEPS

1. configure

2. route maximum {ipv4 | ipv6} value

3. end

commit

Implementing Static Routes on Cisco IOS XR Software

How to Implement Static Routes on Cisco IOS XR Software

RC-254

Cisco IOS XR Routing Configuration Guide

DETAILED STEPS

Command or Action Purpose

Step 1 configure

Example:

RP/0/RP0/CPU0:router# configure

Enters global configuration mode.

Step 2 route maximum {ipv4 | ipv6}

value

Example:

RP/0/RP0/CPU0:router(config)# route maximum

ipv4 10000

Changes the maximum number of allowable static routes.

•Specify IPv4 or IPv6 address prefixes.

•Specify the maximum number of static routes for the

given address family. The range is from 1 to 128000.

•This example sets the maximum number of static IPv4

routes to 10000.

Step 3 end

commit

Example:

RP/0/RP0/CPU0:router(config)# end

RP/0/RP0/CPU0:router(config)# commit

Saves configuration changes.

•When you issue the end command, the system prompts

you to commit changes:

Uncommitted changes found, commit them before

exiting(yes/no/cancel)?

[cancel]:

–

Entering yes saves configuration changes to the

running configuration file, exits the configuration

session, and returns the router to EXEC mode.

–

Entering no exits the configuration session and

returns the router to EXEC mode without

committing the configuration changes.

–

Entering cancel leaves the router in the current

configuration session without exiting or

committing the configuration changes.

•Use the commit command to save the configuration

changes to the running configuration file and remain

within the configuration session.

Implementing Static Routes on Cisco IOS XR Software

Configuration Examples

RC-255

Cisco IOS XR Routing Configuration Guide

Configuration Examples

This section provides the following configuration examples:

•Configuring Traffic Discard: Example

•Configuring a Fixed Default Route: Example

•Configuring a Floating Static Route: Example

Configuring Traffic Discard: Example

Configuring a static route to point at interface null 0 may be used for discarding traffic to a particular

prefix. For example, if it is required to discard all traffic to prefix 2001:0DB8:42:1/64, the following

static route would be defined:

configure

route ipv6 unicast 2001:0DB8:42:1::/64 null 0

end

Configuring a Fixed Default Route: Example

A default static route is often used in simple router topologies. In the following example, a router is

configured with an administrative distance of 110.

configure

route ipv4 unicast 10.0.0.0/8 172.20.16.6 110

end

Configuring a Floating Static Route: Example

A floating static route often is used to provide a backup path if connectivity fails. In the following

example, a router is configured with an administrative distance of 201.

configure

route ipv6 unicast 2001:0DB8::/32 2001:0DB8:3000::1 201

end

Where to Go Next

For additional information on static routes, routing protocols, and RIB, consult the following

publications:

•Implementing and Monitoring RIB on Cisco IOS XR Software

•Implementing BGP on Cisco IOS XR Software

•Implementing IS-IS on Cisco IOS XR Software

•Implementing OSPF on Cisco IOS XR Software

•Implementing OSPFv3 on Cisco IOS XR Software

•RIB Commands on Cisco IOS XR Software

Implementing Static Routes on Cisco IOS XR Software

Additional References

RC-256

Cisco IOS XR Routing Configuration Guide

Additional References

The following sections provide references related to implementing static routes on Cisco IOS XR

software.

Related Documents

Standards

MIBs

RFCs

Technical Assistance

Related Topic Document Title

Static routes commands: complete command syntax,

command modes, command history, defaults, usage

guidelines, and examples

Static and Utility Routing Commands on Cisco IOS XR Software,

Release 3.2

Standards Title

No new or modified standards are supported by this

feature, and support for existing standards has not been

modified by this feature.

—

MIBs MIBs Link

There are no applicable MIBs for this module. To locate and download MIBs for selected platforms using

Cisco IOS XR software, use the Cisco MIB Locator found at the

following URL:

http://cisco.com/public/sw-center/netmgmt/cmtk/mibs.shtml

RFCs Title

No new or modified RFCs are supported by this

feature, and support for existing RFCs has not been

modified by this feature.

—

Description Link

The Cisco Technical Support website contains

thousands of pages of searchable technical content,

including links to products, technologies, solutions,

technical tips, and tools. Registered Cisco.com users

can log in from this page to access even more content.

http://www.cisco.com/techsupport

HC Cisco IOS XR Interface and Hardware Component

Configuration Guide

IC Cisco IOS XR IP Addresses and Services Configuration Guide

MCC Cisco IOS XR Multicast Configuration Guide

MPC Cisco IOS XR MPLS Configuration Guide

QC Cisco IOS XR Modular Quality of Service Configuration

Guide

RC Cisco IOS XR Routing Configuration Guide

SC Cisco IOS XR System Security Configuration Guide

SMC Cisco IOS XR System Management Configuration Guide

RC-257

Cisco IOS XR Routing Configuration Guide

INDEX

address family command RC-5

address-family command (IS-IS) RC-96

adjacencies, tuning RC-113

administrative distance RC-197

advertisement-interval command RC-56

aggregate-address command RC-44

apply command RC-223

Area Border Routers (ABRs) RC-134

area command RC-146

attached bit on an IS-IS instance RC-90

authentication

MD5 (OSPFv2) RC-135

route, key rollover (OSPFv2) RC-136

strategies RC-136

authentication, configuring (OSPFv2) RC-155

authentication command (OSPFv2) RC-156

authentication message-digest command RC-162

Autonomous System Boundary Routers (ASBRs) RC-134

autonomous systems RC-132

backbone area RC-133

bestpath algorithm RC-18

BGP (Border Gateway Protocol)

bestpath algorithm RC-18

configuration

grouping RC-5

inheriting RC-7

description RC-1

functional overview RC-2

inheritance, monitoring RC-11

local next-hop addresses, validating RC-4

multiprotocol RC-21

neighbors, maximum limits on RC-3

policy attach points

dampening RC-225

default originate RC-225

neighbor export RC-226

neighbor import RC-226

network RC-227

redistribute RC-227

show bgp RC-228

table policy RC-229

policy attach points, aggregation RC-224

router identifier

router identifier RC-3

routing policy

enforcing RC-16

update groups

description RC-18

example RC-77

bgp bestpath as-path ignore command RC-40

bgp bestpath compare-routerid command RC-41

bgp bestpath med always command RC-40

bgp bestpath med confed command RC-40

bgp bestpath med missing-as-worst command RC-40

bgp confederation identifier command RC-32

bgp confederation peers command RC-33

Index

RC-258

Cisco IOS XR Routing Configuration Guide

bgp dampening command RC-49

bgp default local-preference command RC-36

bgp global address family submode RC-5

aggregate-address command RC-44

bgp dampening command RC-49

distance bgp command RC-54

network command RC-42

redistribute command RC-47

See address family command

table-policy command RC-53

bgp neighbor address family submode RC-5

next-hop self command RC-65

route-policy (BGP) command RC-63

route-policy command RC-31

route-reflector-client command RC-61

See neighbor address family command

send-community-ebgp command RC-67

soft-reconfiguration inbound always command RC-69

weight command RC-39

bgp neighbor command RC-5

bgp neighbor group submode RC-6, RC-56

advertisement-interval command RC-56

description command RC-56

dmz-link-bandwidth command RC-56

ebgp-multihop command RC-56

local-as command RC-56

password accept command RC-57

password-disable command RC-57

receive-buffer-size command RC-57

See neighbor group command

See neighbor-group command

send-buffer-size command RC-57

timers command RC-57

ttl-security command RC-57

update-source command RC-57

bgp neighbor submode RC-5

See bgp neighbor command

shutdown command RC-70

use command RC-58

bgp redistribute-internal command RC-45

bgp router submode RC-5

bgp bestpath as-path ignore command RC-40

bgp bestpath compare-routerid command RC-41

bgp bestpath med always command RC-40

bgp bestpath med confed command RC-40

bgp bestpath med missing-as-worst command RC-40

bgp confederation identifier command RC-32

bgp confederation peers command RC-33

bgp default local-preference command RC-36

bgp redistribute-internal command RC-45

default-metric command RC-37

See router bgp command

timers bgp command RC-34

bgp session group submode RC-6

BGP update groups example RC-77

circuit-type command RC-97

clear bgp flap-statistics command RC-50

clear bgp flap-statistics reexp command RC-51

clear bgp flap-statistics route-policy command RC-51

clear bgp soft in command RC-71

clear bgp soft out command RC-72

clear ospf command RC-181

clear ospfv3 command RC-181

csnp-interval command RC-104

dampening, route RC-23

dead interval command RC-152

default address family RC-15

default-cost command RC-149

default-information originate command RC-121

default-metric command RC-37

description command RC-56

distance bgp command RC-54

Index

RC-259

Cisco IOS XR Routing Configuration Guide

distance command RC-121

dmz-link-bandwidth command RC-56

Draft-ietf-idr-bgp4-24.txt, BGP RC-80, RC-244

Draft-ietf-idr-bgp4-mib-15.txt, BGP RC-80

draft-ietf-idr-cease-subcode-05.txt RC-80

Draft-ietf-isis-igp-p2p-over-lan-05.txt, Point-to-point

operation over LAN RC-124

Draft-ietf-isis-ipv6-05.txt, Routing IPv6 with

IS-IS RC-124

Draft-ietf-isis-restart-04.txt, Restart Signalling for

IS-IS RC-124

Draft-ietf-isis-traffic-05.txt, IS-IS Extensions for Traffic

Engineering RC-124

Draft-ietf-isis-wg-multi-topology-06.txt, M-ISIS

Multi Topology (MT) Routing in IS-IS RC-124

ebgp-multihop command RC-56

end-policy command RC-30

EXEC mode RC-13

clear bgp flap statistics command RC-50

clear bgp flap statistics reexp command RC-51

clear bgp flap statistics route-policy command RC-51

clear bgp soft in command RC-71

clear bgp soft out command RC-72

clear ospf command RC-181

clear ospfv3 command RC-181

show bgp af-group command RC-12, RC-13

show bgp cidr-only command RC-74

show bgp community command RC-74

show bgp count-only command RC-74

show bgp flap-statistics command RC-50

show bgp flap statistics reexp command RC-50

show bgp flap statistics route-policy command RC-50

show bgp inheritance command RC-12

show bgp neighbor command RC-11

show bgp neighbor-group command RC-14, RC-75

show bgp neighbors command RC-74

show bgp paths command RC-75

show bgp reexp command RC-74

show bgp summary command RC-75

show isis adjacency command RC-101

show isis adjacency-log command RC-101

show isis command RC-93

show isis database command RC-105

show isis database-log command RC-105

show isis interface command RC-116

show isis lsp-log command RC-105

show isis mpls command RC-112

show isis mpls traffic-eng adjacency-log

command RC-112

show isis mpls traffic-eng advertisements

command RC-112

show isis neighbors command RC-116

show isis spf-log command RC-118

show isis topology command RC-97

show running-config command RC-107

graceful-restart helper command RC-142

graceful-restart interval command RC-142

graceful-restart lifetime command RC-142

hello-interval (IS-IS) command RC-114

hello interval (OSPF) command RC-152

hello-multiplier command RC-114

hello-padding command RC-114

hello-password command RC-110, RC-115

ignore-lsp-errors command RC-104

inheritance

configurations (BGP) RC-7

monitoring RC-11

Index

RC-260

Cisco IOS XR Routing Configuration Guide

interior routers RC-134

IPv6

IS-IS support

multitopology RC-88

single-topology RC-87

RIB support RC-197

routing RC-86

IS-IS (Intermediate System-to-Intermediate System)

adjacencies, tuning RC-113

attached bit on an instance RC-90

authentication, configuring RC-108

Cisco IOS and Cisco IOS XR software differences,

configuration

grouped RC-85

configuration

grouped configuration RC-85

Level 1 or Level 2 routing RC-91

multitopology RC-98

restrictions RC-84

single topology RC-93

customizing routes RC-119

default routes RC-90

description RC-83

enabling RC-91, RC-250, RC-251, RC-253

enabling multicast-intact RC-118

functional overview RC-85

grouped configuration RC-85

IPv6 routing RC-86

Level 1 or Level 2 routing, configuration RC-91

LSP flooding

controlling RC-102

lifetime maximum RC-87

limiting RC-86

MPLS TE

configuring RC-110

description RC-89

multi-instance IS-IS RC-89

multitopology, configuring RC-98

nonstop forwarding RC-88

configuring RC-106

overload bit

configuring RC-87

on router RC-89

policy attach points

redistribute RC-234

restrictions, configuring RC-84

set SPF interval RC-116

single topology

configuring RC-93

single-topology

IPv6 support RC-87

isis router submode

router isis command RC-100

ispf command RC-117

ispf startup-delay command RC-117

is-type command RC-92

link-state advertisement (LSA)

OSPFv2 RC-137

OSPFv3 RC-129, RC-137, RC-143

local-as command RC-56

log adjacency changes command RC-114, RC-147

lsp-check-interval command RC-103

LSP flooding

controlling RC-102

lifetime maximum RC-87

limiting RC-86

mesh group configuration RC-87

on specific interfaces RC-87

lsp-gen-interval command RC-103

lsp-interval command RC-104

lsp-mtu command RC-103

lsp-password command RC-109

lsp-refresh-interval command RC-103

Index

RC-261

Cisco IOS XR Routing Configuration Guide

maximum-paths command RC-121

max-lsp-lifetime command RC-103

mesh-group command RC-104

message-digest-key command RC-156

metric-style wide command RC-112

MPLS TE (Multiprotocol Label Switching traffic

engineering) configuring

IS-IS RC-110

OSPFv2 RC-175

mpls traffic-eng area command RC-176

mpls traffic-eng command RC-111

mpls traffic-eng router-id command RC-112, RC-177

multicast-intact

IS-IS RC-90

OSPFv2 RC-144

multi-instance IS-IS RC-89

multiprotocol BGP RC-21

multitopology

configuring RC-98

example RC-123

NBMA networks RC-135

neighbor address family command RC-5

neighbor command RC-5

neighbor command (OSPFv2, OSPFv3) RC-153

neighbor-group command RC-56

neighbors

adjacency (OSPFv2) RC-136

maximum limits (BGP) RC-3

net command RC-92, RC-251, RC-252, RC-254

network command RC-42, RC-152

next-hop-self command RC-65

nonstop forwarding, configuring (OSPFv2) RC-173

not-so-stubby area RC-133

nsf command RC-106

nsf interface-expires command RC-107

nsf interface-timer command RC-107

nsf interval command RC-175

nsf lifetime command RC-107

nsg enforce global command RC-174

nssa command RC-149

ospf area configuration submode

dead-interval command RC-152

default-cost command RC-149

hello interval command RC-152

interface command RC-146

network command RC-152

nssa command RC-149

range command RC-165

stub command RC-149

ospf area submode

authentication message-digest command RC-162

virtual-link command RC-162

ospf interface configuration submode

log adjacency changes RC-147

neighbor command RC-153

OSPFv2 (Open Shortest Path First Version 2)

authentication, configuring RC-155

Cisco IOS XR OSPFv3 and OSPFv2 differences RC-131

CLI (command-line interface) inheritance RC-131

configuration

MPLS TE RC-175

neighbors, nonbroadcast networks RC-150

configuration and operation, verifying RC-180

description RC-127

Designate Router (DR) RC-136

enabling RC-145

functional overview RC-129

instance and router ID RC-134

LSA

controlling the frequency RC-158

Index

RC-262

Cisco IOS XR Routing Configuration Guide

on an OSPF ABR RC-164

types RC-137

MD5 authentication RC-135

MPLS TE, configuring RC-175

neighbors, adjacency RC-136

neighbors, nonbroadcast networks, configuring RC-150

nonstop forwarding

configuring RC-173

description RC-140

policy attach points

default originate RC-231

redistribute RC-231, RC-233

route authentication methods

key rollover RC-136

MD5 RC-135

plain text RC-135

strategies RC-136

route redistribution

configuring RC-166

description RC-139

Shortest Path First (SPF) throttling

configuring RC-170

description RC-139

stub and not-so-stubby area types, configuring RC-147

supported OSPF network types

NBMA networks RC-135

point to point networks RC-135

virtual link

creating RC-160

transit area RC-138

OSPFv2 (Open Shortest Path Fisrt version 2)

enabling multicast-intact RC-186

OSPFv3 (Open Shortest Path First Version 3) RC-170

addresses, importing RC-131

Cisco IOS XR OSPFv3 and OSPFv2 differences RC-131

CLI inheritance RC-131

configuration

neighbors, nonbroadcast networks RC-150

SPF throttling RC-170

configuration and operation, verifying RC-180

description RC-127

enabling RC-145

functional overview RC-129

instance and router ID RC-134

load balancing RC-141

LSA

controlling frequency RC-158

on an OSPF ABR RC-164

types RC-137

neighbors

nonbroadcast networks, configuring RC-150

policy attach points

default originate RC-232

redistribute RC-231, RC-233

routes, redistribute RC-166

SPF (Shortest Path First) throttling configuring RC-170

stub and not-so-stubby area types, configuring RC-147

virtual link, description RC-138

ospfv3 area configuration submode

dead-interval command RC-152

default-cost command RC-149

hello interval command RC-152

interface command RC-146

network command RC-152

nssa command RC-149

range command RC-165

stub command RC-149

OSPFv3 Graceful Restart feature RC-141

adjacency RC-143

displaying information RC-186

ospfv3 interface configuration submode

log adjacency changes RC-147

neighbor command RC-153

overload bit

configuration RC-87

on router RC-89

Index

RC-263

Cisco IOS XR Routing Configuration Guide

password accept command RC-57

password-disable command RC-57

point-to-point networks RC-135

policy, modifying

attached RC-235

nonattached RC-235

range command RC-165

receive-buffer-size command RC-57

redistribute command RC-47, RC-168

redistribute isis command RC-121

retransmit-interval command RC-104

retransmit-throttle-interval command RC-104

RFC 1142, OSI IS-IS Intra-domain Routing

Protocol RC-125

RFC 1195, Use of OSI IS-IS for Routing in TCP/IP and

Dual Environments RC-125

RFC 1587, Not So Stubby Area (NSSA) RC-193

RFC 1793, OSPF over demand circuit RC-193

RFC 1997, BGP Communities Attribute RC-80

RFC 2328, OSPF Version 2 RC-130, RC-193

RFC 2385, Protection of BGP Sessions via the TCP MD5

Signature Option RC-80

RFC 2439, BGP Route Flap Damping RC-80

RFC 2545, Use of BGP-4 Multiprotocol Extensions for

IPv6 Inter-Domain Routing RC-80

RFC 2740, OSPFv3 RC-193

RFC 2740 OSPFv3 RC-130

RFC 2763, Dynamic Hostname Exchange Mechanism for

IS-IS RC-125

RFC 2796, BGP Route Reflection - An Alternative to Full

Mesh IBGP RC-80

RFC 2858, Multiprotocol Extensions for BGP-4 RC-80

RFC 2918, Route Refresh Capability for BGP-4 RC-80

RFC 2966, Domain-wide Prefix Distribution with

Two-Level IS-IS RC-125

RFC 2973, IS-IS Mesh Groups RC-125

RFC 3065, Autonomous System Confederations for

BGP RC-81

RFC 3277, IS-IS Transient Blackhole Avoidance RC-125

RFC 3373, Three-Way Handshake for IS-IS Point-to-Point

Adjacencies RC-125

RFC 3392, Capabilities Advertisement with BGP-4 RC-81

RFC 3567, IS-IS Cryptopgraphic Authentication RC-125

RFC 3623, OSPFv3 RC-193

RIB (Routing Information Base)

administrative distance RC-197

data structures in BGP and other protocols RC-196

deploying RC-198

description RC-195

examples RC-200

functional overview RC-196

IPv4 and IPv6 support RC-197

monitoring RC-198

prerequisites RC-196

route dampening RC-23

route-policy (BGP) command RC-31, RC-63

route-policy command RC-29, RC-62

route-policy pass-all command RC-16

route policy submode RC-29

end-policy command RC-30

See route-policy command

router bgp command RC-5

router bgp neighbor group address family configuration

mode

address family command RC-6

route redistribution (OSPFv2, OSPFv3) RC-139

route-reflector-client command RC-61

route reflectors RC-24

router-id command RC-146

router isis address family submode

default-information originate command RC-121

distance command RC-121

ispf command RC-117

ispf startup-delay command RC-117

maximum-paths command RC-121

metric-style wide command RC-112

Index

RC-264

Cisco IOS XR Routing Configuration Guide

mpls traffic-eng command RC-111

mpls traffic-eng router-id command RC-112

redistribute isis command RC-121

set-attached-bit command RC-122

single-topology command RC-96

spf-interval command RC-117

summary-prefix command RC-121

router isis command RC-100

router isis configuration submode

address-family command RC-96

ignore-lsp-errors command RC-104

is-type command RC-92

log adjacency changes command RC-114

lsp-check-interval command RC-103

lsp-gen-interval command RC-103

lsp-mtu command RC-103

lsp-password command RC-109

lsp-refresh-interval command RC-103

max-lsp-lifetime command RC-103

net command RC-92, RC-251, RC-252, RC-254

nsf command RC-106

nsf interface-expires command RC-107

nsf interface-timer command RC-107

nsf lifetime command RC-107

set-overload-bit command RC-120

router isis interface configuration submode

address-family command RC-97

circuit-type command RC-97

csnp-interval command RC-104

hello-interval command RC-114

hello-multiplier command RC-114

hello-padding command RC-114

hello-password command RC-110, RC-115

ipv4 address command RC-95

ipv6 address command RC-95

ipv6 enable command RC-95

lsp-interval command RC-104

mesh-group command RC-104

retransmit-interval command RC-104

retransmit-throttle-interval command RC-104

router isis interface submode

mesh-group command RC-104

router ospf command RC-146

router ospf configuration submode RC-146

area command RC-146

authentication command RC-156

message-digest-key command RC-156

mpls traffic-eng area command RC-176

mpls traffic-eng router-id command RC-177

nsf interval command RC-175

redistribute command RC-168

router-id command RC-146

summary-prefix command RC-169

timers lsa gen-interval command RC-159

timers lsa group-pacing command RC-160

timers lsa min-interval command RC-159

timers throttle spf command RC-171

router ospf configuration submode command

nsf command RC-174

router ospf submode

nsf enforce global RC-174

router ospfv3 command RC-146

router ospfv3 configuration submode

area command RC-146

redistribute command RC-168

router-id command RC-146

summary-prefix command RC-169

timers lsa gen-interval command RC-159

timers lsa group-pacing command RC-160

timers lsa min-interval command RC-159

timers throttle spf command RC-171

routes

customizing (IS-IS) RC-119

default

IS-IS RC-90

redistribute (OSPFv2, OSPFv3) RC-166

redistribute IS-IS routes example RC-123

routing components

Index

RC-265

Cisco IOS XR Routing Configuration Guide

Area Border Routers (ABRs) RC-134

Autonomous System Boundary Routers

(ASBRs) RC-134

autonomous systems RC-132

backbone area RC-133

Designated Router (DR) RC-136

interior routers RC-134

not-so-stubby area RC-133

stub area RC-133

routing domain confederation RC-24

routing policy RC-16

attaching to BGP neighbor RC-238

configuration elements, editing RC-235

defining RC-237

defining (example) RC-241

enforcing, BGP RC-16

implementing

prerequisites RC-206

inbound (example) RC-242

modifying RC-240

modular inbound (example) RC-243

statements

action RC-221

disposition RC-220

elseif RC-221

if RC-221

remark RC-219

RPL (routing policy language)

Boolean operators, types RC-222

components RC-211

overview RC-206

policy

attributes

modification RC-216

parameterization RC-214

Boolean operator precedence RC-215

configuration basics RC-213

default drop disposition RC-217

definitions RC-213

statement processing RC-217

statements, types RC-219

verification RC-218

structure

as-path-set, inline set form RC-208

as-path-set, named set form RC-208

community-set, inline set form RC-209

community-set, named set form RC-209

extended community set, inline form RC-210

extended community set, named form RC-209

names RC-207

prefix-set RC-210

sets RC-207

send-buffer-size command RC-57

send-community-ebgp command RC-67

set-attached-bit command RC-122

set-overload-bit command RC-120

show bgp af-group command RC-12, RC-13

show bgp cidr-only command RC-74

show bgp community command RC-74

show bgp count-only command RC-74

show bgp flap-statistics command RC-50

show bgp flap-statistics reexp command RC-50

show bgp flap-statistics route-policy command RC-50

show bgp inheritance command RC-12

show bgp neighbor command RC-11

show bgp neighbor-group command RC-14, RC-75

show bgp neighbors command RC-74

show bgp paths command RC-75

show bgp reexp command RC-74

show bgp session-group command RC-13

show bgp summary command RC-75

show ip route connected command RC-201

show isis adjacency command RC-101

show isis adjacency-log command RC-101

show isis command RC-93

Index

RC-266

Cisco IOS XR Routing Configuration Guide

show isis database command RC-105

show isis database-log command RC-105

show isis interface command RC-116

show isis lsp-log command RC-105

show isis mpls command RC-112

show isis mpls traffic-eng adjacency-log

command RC-112

show isis mpls traffic-eng advertisements

command RC-112

show isis neighbors command RC-116

show isis spf-log command RC-118

show isis topology command RC-97

show ospf command RC-162

show ospfv3 command RC-162

show running-config command RC-107

shutdown command RC-70

single-topology

command RC-96

configuring example RC-122

IPv6 support RC-87

set SPF interval RC-116

soft-reconfiguration inbound always command RC-69

spf-interval command RC-117

SPF throttling, configuring

OSPFv2 (Open Shortest Path First Version 2) RC-170

static route

Cisco IOS static route and Cisco IOS XR static route

differences RC-247

stub area RC-133

stub area types, configuring (OSPFv3) RC-147

stub command RC-149

summary-prefix command RC-121, RC-169

table-policy command RC-53

timers bgp command RC-34

timers command RC-57

timers lsa gen-interval command RC-159

timers lsa group-pacing command RC-160

timers lsa min-interval command RC-159

timers throttle spf command RC-171

ttl-security command RC-57

update groups

BGP configuration RC-18

BGP update generation RC-18

monitor RC-75

update-source command RC-57

use command RC-58

virtual link

transit area (OSPFv2) RC-138

virtual-link command RC-162

weight command RC-39

Cisco Systems Ios Xr Users Manual

IOS XR to the manual 3bebaf9c-1005-4ee8-b7c8-c2df46a91b7f

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