Digi Application Note 34 Users Manual N
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2015-02-04
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Application Note 34 Configuring ADSL to backup to PSTN/ISDN with automatic testing and recovery back to ADSL. UK Support 29 December 2009 1 Contents 1 2 3 Introduction ............................................................................................................................................... 2 1.1 Outline ............................................................................................................................................... 2 1.2 Assumptions ...................................................................................................................................... 2 1.3 Corrections ........................................................................................................................................ 3 1.4 Version ............................................................................................................................................... 3 Configuration ............................................................................................................................................. 4 2.1 Configure PPP 1 (ADSL) ...................................................................................................................... 4 2.2 Configure PPP 4 (PSTN)...................................................................................................................... 6 2.3 Configure the Default Routes ............................................................................................................ 8 2.4 Configure the Firewall ....................................................................................................................... 9 2.5 Save configuration ........................................................................................................................... 10 Testing ..................................................................................................................................................... 11 3.1 4 Simulate a failure ............................................................................................................................. 11 Configuration Files ................................................................................................................................... 11 4.1 Digi Transport Configuration Files ................................................................................................... 11 4.2 Digi Transport Firmware Versions ................................................................................................... 12 1 INTRODUCTION 1.1 Outline The document describes how to configure a Digi Transport router to fail over to PSTN when there is a problem with the main ADSL connection. Once the ADSL connection is working again the router will test it by sending pings and then revert back to ADSL and drop the PSTN connection. This application note uses PPP 4 (PSTN) as the failover interface, however, if the router being configured has ISDN, simply configure PPP 2 (ISDN) instead of PPP 4. The same configuration can be applied to the ISDN interface. For failover from ADSL to a cellular network, please see Application Note 34a as the configuration is slightly different. 1.2 Assumptions This guide has been written for use by technically competent personnel with a good understanding of the communications technologies used in the product, and of the requirements for their specific application. Configuration: This application note assumes that the router will be connecting to a cellular network. This application note applies to; Models shown: Digi Transport DR64 router with ADSL & PSTN running firmware version 5081. Other Compatible Models: All Digi Transport products. Firmware versions: 4905 or later. 2 Configuration: This Application Note assumes that the Digi Transport router is already configured with a working ADSL connection through PPP 1. 1.3 Corrections Requests for corrections or amendments to this application note are welcome and should be addressed to: uksupport@digi.com Requests for new application notes can be sent to the same address. 1.4 Version Version Number Status 1.0 Published 1.1 Re-branded to Digi Transport 3 2 CONFIGURATION 2.1 Configure PPP 1 (ADSL) This PPP interface should already be configured for use with the ISP. You should confirm that you have a working ADSL connection before proceeding with this configuration. The PPP 1 interface needs to be configured to be “always on”. The inactivity timer should be set to 0. Configuration - Interfaces > PPP > PPP 0 - 4 > PPP 1 > Standard Parameter Setting Description Always on mode ON Configures interface as always on Inactivity timeout (s): 0 Interface is always connected and active Click OK PPP 1 should be configured to generate ICMP requests that the firewall can monitor and use to detect when the ADSL connection has a problem. It is also necessary to configure a settling time on the interface. The settling time is a parameter that prevents the Digi Transport from using the interface until it has been up for the specified number of seconds. This delay is required so that any ICMP echo requests (used for testing the interface) are not sent so soon after the interface has come up that the ISP drops the reply packet. (ISP routing tables are often not updated within the first few seconds of an interface coming up. Sending packets immediately often causes the reply to these packets to be dropped.) Configuration - Interfaces > PPP > PPP 0 - 4 > PPP 1 > Advanced Parameter Setting Description Ping request interval Only send PINGs when interface is in service 10 Send ICMP requests every x seconds YES Do not send ICMP requests if using cellular PING IP address 1.2.3.4 Settling time (*100ms) 100 A public IP address that you can ping to check connectivity via ADSL Do not send 1st ping until 10 seconds after interface has come up 4 Click OK 5 2.2 Configure PPP 4 (PSTN) It will be necessary to configure PPP 4 as an outbound interface as the default is for the interface to accept incoming calls. Then ISP configuration will be added. Navigate to the following location: Configuration - Interfaces > PPP > PPP 0 - 4 > PPP 4 > Standard Scroll to the bottom of the page and click “Load dialling defaults”. The PPP 4 configuration needs to be configured to be “always on” and have a power up delay of 60 seconds to allow the ADSL connection to come up and be the primary connection. The interface will also be configured for use with an ISP, enter the details as shown in the tables below. Parameter Setting Description Dial-out number 0845 1400101 Replace with the number for your ISP Use GPRS/PSTN/external modem PSTN Use internal PSTN modem **Use W-WAN/external modem No Use internal ISDN modem Username User Replace with your dial up username Password Pass Replace with your dial up password Always on mode ON Power up AODI delay (s) 60 Inactivity timeout (s) 0 Local IP address 0.0.0.0 Interface should always be active Timer to allow main ADSL connection to come up before this one is activated Keep interface in service even if no data passes through interface Your ISP will normally assign an IP address automatically ** Only applies if configuring ISDN, not PSTN 6 Click OK Configuration - Interfaces > PPP > PPP 0 - 4 > PPP 4 > Advanced The PSTN interface needs to be configured so that if PPP 1 (ADSL) is up and in service (i.e. passing data) then this interface is not allowed to initiate a connection. Parameter Inhibit auto-activation when these PPPs are active Inhibit mode Setting 1 Inhibit if other PPP is active and not OOS Description Inhibit auto-activation of PPP 4 when PPP 1 is active Only inhibit if PPP 1 is passing data 7 Click OK 2.3 Configure the Default Routes It is necessary to configure two default routes, one for PPP 1 and one for PPP 4. The PPP 1 default route needs to be set so PPP 4 is deactivated when PPP 1 returns to service after a successful recovery. Configuration - Routing > Default Route 0 Parameter Setting Interface PPP Interface # 1 Deactivate interface PPP Deactivate interface # 4 Description Default route 0 is via PPP 1 PPP 4 will be deactivated when this route comes back into service after an outage Click OK The configuration of default route 1 should be configured as shown. Configuration - Routing > Default Route 1 Parameter Setting Interface PPP Interface # 4 Deactivate interface None Deactivate interface # 0 Description Default route 1 is via PPP 4 This will allow for recovery to ADSL 8 Click OK 2.4 Configure the Firewall The firewall should be configured to monitor the ICMP requests generated by PPP 1. If the firewall detects that 3 consecutive ICMP echo requests have failed, it will take PPP 1 out of service and deactivated thus allowing PPP 4 to come up. The IP address in the firewall rule must be the IP address that PPP 1 is sending pings to. The recovery code will then test the ADSL connection before bringing it back into service. When the recovery is successful and PPP 1 comes back into service, PPP 4 will be deactivated. Configuration – Security > Firewall Insert the following 2 rules: Rule 1 pass out break end on ppp 1 proto icmp from any to 1.2.3.4 icmp-type echo inspect-state oos 10 t=3 c=3 d=3 r=ping,10,5 rd=1 dt=1 Rule 2 Pass break end Save the firewall rules by clicking the “Save (fw -> fw.txt)” button. Rule 1 explained: pass out break end on PPP 1 – allow traffic outbound from PPP 1 proto icmp from any to 1.2.3.4 icmp-type echo – allow pings out to 1.2.3.4 9 inspect-state – monitor the pings for echo replies and allow them back in oos 10 t=3 c=3 d=3 – if 3 consecutive pings fail, deactivate PPP 1 and start recovery procedures after 10 seconds. This 10 second timer could be increased (by editing the firewall rule) to prevent the Digi Transport from switching rapdily between PPP 1 and PPP 4 in the case where PPP 1 works intermitantly. This “oos 10” can be thought of as a de-bounce timer in the context of this application note. r=ping,10,5 rd=1 dt=1 – during recovery, test the link every 10 seconds with a ping, allow 5 seconds for the response to each ping, if the recovery fails deactivate the interface and deactivate the link before trying again Rule 2 then allows all other traffic through. For a more detailed explanation of the above firewall keywords refer to the Sar/OS reference manual “ftp://ftp1.digi.com/support/documentation/Digi Transport and Sarian User Guide.pdf” Finally turn the firewall on for PPP 1 to activate the ICMP monitoring and recovery. Configuration - Interfaces > PPP > PPP 0 - 4 > PPP 1 > Standard Parameter Setting Description Firewall ON Switches the firewall on for this interface Click OK 2.5 Save configuration Save your configuration as the power up configuration. Administration - Save configuration Click OK Reboot the Digi Transport router (or deactivate PPP 1) so the PPP changes take effect. 10 3 TESTING 3.1 Simulate a failure To test the fail over and recovery you will need to configure the PPP interface to ping a IP address that you can easily stop responding to ICMP requests (either through the use of a firewall or by physically disconnecting it from the network). You will also need to alter the firewall rule so it monitors the same IP address that PPP 1 is pinging. Once you have the IP address configured and the Digi Transport router is up on the main WAN link, remove your test device from the network or adjust the firewall so it stops responding to the ICMP requests from the Digi Transport router. After approximately 30 seconds the router should bring up PPP 4 (the dial-up connection). To confirm that PPP 4 is up and being used you can: • check the entries in Diagnostics - Event Log • click on Diagnostics - Status > PPP > PPP 0 - 4 > PPP 4 > View and check the link is up and has a valid IP address • click on Configuration - Routing > Default Route 0 then scroll to the bottom and click on the button ‘Show IPv4 Routing Table’ to view the routing table which should show PPP 4 with a status of UP and PPP 1 with a status of OOS. • Also for dial-up, the routers OH and CD LED’s should be lit. Once you have confirmed that the router has failed over correctly, re-enable the ICMP response or reconnect the test device to the network. You should notice that after approximately 20 seconds, the router drops the dial-up connection as the main PPP 1 link becomes available again. This will again be shown in the event log, the routing table, the PPP 4 status should show Link Inactive, and the OH & CD LED’s should go out. 4 CONFIGURATION FILES 4.1 Digi Transport Configuration Files This is the relevant parts of the configuration file: eth 0 IPaddr "10.1.51.2" eth 0 mask "255.255.0.0" def_route def_route def_route def_route def_route def_route def_route def_route ppp ppp ppp ppp ppp ppp ppp ppp ppp ppp ppp ppp ppp ppp ppp 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 0 0 0 0 1 1 2 4 ll_ent "PPP" ll_add 1 deact_ent "PPP" deact_add 4 ll_ent "PPP" ll_add 4 ll_add 3 ll_add 4 IPaddr "0.0.0.0" username "user@isp.com" epassword "encrypted" timeout 0 aodion 1 autoassert 1 do_nat 2 firewall ON pingip "1.2.3.4" pingint 10 pingis ON l1iface "AAL" ipanon ON pppanon ON settledly 100 ppp 4 IPaddr "0.0.0.0" 11 ppp ppp ppp ppp ppp ppp ppp ppp ppp ppp ppp 4 4 4 4 4 4 4 4 4 4 4 username "user@isp.com" epassword "encrypted" phonenum " 0845 1400101" use_modem 3 aodion 1 pwr_dly 60 autoassert 1 ipsec 1 l1iface "Default" inhibitno "1" inhmode 1 ana ana ana ana ana ana 0 0 0 0 0 0 anon ON l1on ON xoton OFF lapdon 0 lapbon 0 logsize 45 4.2 Digi Transport Firmware Versions This is the firmware \ hardware information: Digi TransPort DR6410-HIA DSL2/2+ Router Ser#:60000 Software Build Ver5081. Nov 17 2009 17:49:53 8W ARM Bios Ver 5.76 v31 197MHz B128-M128-F300-O1841d1,0 MAC:00042d000000 Async Driver Revision: 1.19 Int clk Ethernet Hub Driver Revision: 1.11 ISDN ST 21150 Driver Revision: 1.7 Firewall Revision: 1.0 EventEdit Revision: 1.0 Timer Module Revision: 1.1 AAL Revision: 1.0 ADSL Revision: 1.0 (B)USBHOST Revision: 1.0 SNA o IP Revision: 1.02 L2TP Revision: 1.10 PPTP Revision: 1.00 TACPLUS Revision: 1.00 MySQL Revision: 0.01 LAPB Revision: 1.12 LAPD Revision: 1.16 TEI Management Revision: 1.6 BRI Call Control Layer Revision: 1.11 X25 Layer Revision: 1.19 MACRO Revision: 1.0 PAD Revision: 1.4 X25 Switch Revision: 1.7 V120 Revision: 1.16 TPAD Interface Revision: 1.12 SCRIBATSK Revision: 1.0 BASTSK Revision: 1.0 ARM Sync Driver Revision: 1.18 TCP (HASH mode) Revision: 1.14 TCP Utils Revision: 1.13 PPP Revision: 1.19 WEB Revision: 1.5 SMTP Revision: 1.1 FTP Client Revision: 1.5 FTP Revision: 1.4 IKE Revision: 1.0 12 PollANS PPPOE BRIDGE MODEM CC (Option 3G) FLASH Write Command Interpreter SSLCLI OSPF BGP QOS RADIUS Client SSH Server SCP CERT LowPrio Tunnel TEMPLOG OK Revision: Revision: Revision: Revision: Revision: Revision: Revision: Revision: Revision: Revision: Revision: Revision: Revision: Revision: Revision: Revision: Revision: 1.2 1.0 1.1 1.4 1.2 1.38 1.0 1.0 1.0 1.0 1.0 1.0 1.0 1.0 1.0 1.2 1.0 13
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