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| Document Title | NWA1100 UG v 1.00 Ed 1 (July 2008) |
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APPENDIX
Setting up Your Computer’s IP
Address
All computers must have a 10M or 100M Ethernet adapter card and TCP/IP installed.
Windows 95/98/Me/NT/2000/XP, Macintosh OS 7 and later operating systems and all
versions of UNIX/LINUX include the software components you need to install and use TCP/
IP on your computer. Windows 3.1 requires the purchase of a third-party TCP/IP application
package.
TCP/IP should already be installed on computers using Windows NT/2000/XP, Macintosh OS
7 and later operating systems.
After the appropriate TCP/IP components are installed, configure the TCP/IP settings in order
to "communicate" with your network.
If you manually assign IP information instead of using dynamic assignment, make sure that
your computers have IP addresses that place them in the same subnet as the ZyXEL Device’s
LAN port.
Windows 95/98/Me
Click Start, Settings, Control Panel and double-click the Network icon to open the Network
window
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Appendix D Setting up Your Computer’s IP Address
Figure 73 WIndows 95/98/Me: Network: Configuration
Installing Components
The Network window Configuration tab displays a list of installed components. You need a
network adapter, the TCP/IP protocol and Client for Microsoft Networks.
If you need the adapter:
1 In the Network window, click Add.
2 Select Adapter and then click Add.
3 Select the manufacturer and model of your network adapter and then click OK.
If you need TCP/IP:
In the Network window, click Add.
Select Protocol and then click Add.
Select Microsoft from the list of manufacturers.
Select TCP/IP from the list of network protocols and then click OK.
If you need Client for Microsoft Networks:
Click Add.
Select Client and then click Add.
Select Microsoft from the list of manufacturers.
Select Client for Microsoft Networks from the list of network clients and then click
OK.
5 Restart your computer so the changes you made take effect.
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Appendix D Setting up Your Computer’s IP Address
Configuring
1 In the Network window Configuration tab, select your network adapter's TCP/IP entry
and click Properties
2 Click the IP Address tab.
• If your IP address is dynamic, select Obtain an IP address automatically.
• If you have a static IP address, select Specify an IP address and type your
information into the IP Address and Subnet Mask fields.
Figure 74 Windows 95/98/Me: TCP/IP Properties: IP Address
3 Click the DNS Configuration tab.
• If you do not know your DNS information, select Disable DNS.
• If you know your DNS information, select Enable DNS and type the information in
the fields below (you may not need to fill them all in).
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Appendix D Setting up Your Computer’s IP Address
Figure 75 Windows 95/98/Me: TCP/IP Properties: DNS Configuration
4 Click the Gateway tab.
• If you do not know your gateway’s IP address, remove previously installed gateways.
• If you have a gateway IP address, type it in the New gateway field and click Add.
5 Click OK to save and close the TCP/IP Properties window.
6 Click OK to close the Network window. Insert the Windows CD if prompted.
7 Turn on your ZyXEL Device and restart your computer when prompted.
Verifying Settings
1 Click Start and then Run.
2 In the Run window, type "winipcfg" and then click OK to open the IP Configuration
window.
3 Select your network adapter. You should see your computer's IP address, subnet mask
and default gateway.
Windows 2000/NT/XP
1 For Windows XP, click start, Control Panel. In Windows 2000/NT, click Start,
Settings, Control Panel.
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Appendix D Setting up Your Computer’s IP Address
Figure 76 Windows XP: Start Menu
2 For Windows XP, click Network Connections. For Windows 2000/NT, click Network
and Dial-up Connections.
Figure 77 Windows XP: Control Panel
3 Right-click Local Area Connection and then click Properties.
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Appendix D Setting up Your Computer’s IP Address
Figure 78 Windows XP: Control Panel: Network Connections: Properties
4 Select Internet Protocol (TCP/IP) (under the General tab in Win XP) and click
Properties.
Figure 79 Windows XP: Local Area Connection Properties
5 The Internet Protocol TCP/IP Properties window opens (the General tab in
Windows XP).
• If you have a dynamic IP address click Obtain an IP address automatically.
• If you have a static IP address click Use the following IP Address and fill in the IP
address, Subnet mask, and Default gateway fields. Click Advanced.
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Figure 80 Windows XP: Advanced TCP/IP Settings
6 If you do not know your gateway's IP address, remove any previously installed gateways
in the IP Settings tab and click OK.
Do one or more of the following if you want to configure additional IP addresses:
• In the IP Settings tab, in IP addresses, click Add.
• In TCP/IP Address, type an IP address in IP address and a subnet mask in Subnet
mask, and then click Add.
• Repeat the above two steps for each IP address you want to add.
• Configure additional default gateways in the IP Settings tab by clicking Add in
Default gateways.
• In TCP/IP Gateway Address, type the IP address of the default gateway in Gateway.
To manually configure a default metric (the number of transmission hops), clear the
Automatic metric check box and type a metric in Metric.
• Click Add.
• Repeat the previous three steps for each default gateway you want to add.
• Click OK when finished.
7 In the Internet Protocol TCP/IP Properties window (the General tab in Windows
XP):
• Click Obtain DNS server address automatically if you do not know your DNS
server IP address(es).
• If you know your DNS server IP address(es), click Use the following DNS server
addresses, and type them in the Preferred DNS server and Alternate DNS server
fields.
If you have previously configured DNS servers, click Advanced and then the DNS
tab to order them.
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Figure 81 Windows XP: Internet Protocol (TCP/IP) Properties
8 Click OK to close the Internet Protocol (TCP/IP) Properties window.
9 Click OK to close the Local Area Connection Properties window.
10 Turn on your ZyXEL Device and restart your computer (if prompted).
Verifying Settings
1 Click Start, All Programs, Accessories and then Command Prompt.
2 In the Command Prompt window, type "ipconfig" and then press [ENTER]. You can
also open Network Connections, right-click a network connection, click Status and
then click the Support tab.
Macintosh OS 8/9
1 Click the Apple menu, Control Panel and double-click TCP/IP to open the TCP/IP
Control Panel.
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Figure 82 Macintosh OS 8/9: Apple Menu
2 Select Ethernet built-in from the Connect via list.
Figure 83 Macintosh OS 8/9: TCP/IP
3 For dynamically assigned settings, select Using DHCP Server from the Configure: list.
4 For statically assigned settings, do the following:
• From the Configure box, select Manually.
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Appendix D Setting up Your Computer’s IP Address
• Type your IP address in the IP Address box.
• Type your subnet mask in the Subnet mask box.
• Type the IP address of your ZyXEL Device in the Router address box.
5 Close the TCP/IP Control Panel.
6 Click Save if prompted, to save changes to your configuration.
7 Turn on your ZyXEL Device and restart your computer (if prompted).
Verifying Settings
Check your TCP/IP properties in the TCP/IP Control Panel window.
Macintosh OS X
1 Click the Apple menu, and click System Preferences to open the System Preferences
window.
Figure 84 Macintosh OS X: Apple Menu
2 Click Network in the icon bar.
• Select Automatic from the Location list.
• Select Built-in Ethernet from the Show list.
• Click the TCP/IP tab.
3 For dynamically assigned settings, select Using DHCP from the Configure list.
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Figure 85 Macintosh OS X: Network
4 For statically assigned settings, do the following:
• From the Configure box, select Manually.
• Type your IP address in the IP Address box.
• Type your subnet mask in the Subnet mask box.
• Type the IP address of your ZyXEL Device in the Router address box.
5 Click Apply Now and close the window.
6 Turn on your ZyXEL Device and restart your computer (if prompted).
Verifying Settings
Check your TCP/IP properties in the Network window.
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APPENDIX
Wireless LANs
Wireless LAN Topologies
This section discusses ad-hoc and infrastructure wireless LAN topologies.
Ad-hoc Wireless LAN Configuration
The simplest WLAN configuration is an independent (Ad-hoc) WLAN that connects a set of
computers with wireless adapters (A, B, C). Any time two or more wireless adapters are within
range of each other, they can set up an independent network, which is commonly referred to as
an ad-hoc network or Independent Basic Service Set (IBSS). The following diagram shows an
example of notebook computers using wireless adapters to form an ad-hoc wireless LAN.
Figure 86 Peer-to-Peer Communication in an Ad-hoc Network
BSS
A Basic Service Set (BSS) exists when all communications between wireless clients or
between a wireless client and a wired network client go through one access point (AP).
Intra-BSS traffic is traffic between wireless clients in the BSS. When Intra-BSS is enabled,
wireless client A and B can access the wired network and communicate with each other. When
Intra-BSS is disabled, wireless client A and B can still access the wired network but cannot
communicate with each other.
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Appendix E Wireless LANs
Figure 87 Basic Service Set
ESS
An Extended Service Set (ESS) consists of a series of overlapping BSSs, each containing an
access point, with each access point connected together by a wired network. This wired
connection between APs is called a Distribution System (DS).
This type of wireless LAN topology is called an Infrastructure WLAN. The Access Points not
only provide communication with the wired network but also mediate wireless network traffic
in the immediate neighborhood.
An ESSID (ESS IDentification) uniquely identifies each ESS. All access points and their
associated wireless clients within the same ESS must have the same ESSID in order to
communicate.
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Appendix E Wireless LANs
Figure 88 Infrastructure WLAN
Channel
A channel is the radio frequency(ies) used by IEEE 802.11a/b/g wireless devices. Channels
available depend on your geographical area. You may have a choice of channels (for your
region) so you should use a different channel than an adjacent AP (access point) to reduce
interference. Interference occurs when radio signals from different access points overlap
causing interference and degrading performance.
Adjacent channels partially overlap however. To avoid interference due to overlap, your AP
should be on a channel at least five channels away from a channel that an adjacent AP is using.
For example, if your region has 11 channels and an adjacent AP is using channel 1, then you
need to select a channel between 6 or 11.
RTS/CTS
A hidden node occurs when two stations are within range of the same access point, but are not
within range of each other. The following figure illustrates a hidden node. Both stations (STA)
are within range of the access point (AP) or wireless gateway, but out-of-range of each other,
so they cannot "hear" each other, that is they do not know if the channel is currently being
used. Therefore, they are considered hidden from each other.
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Appendix E Wireless LANs
Figure 89 RTS/CTS
When station A sends data to the AP, it might not know that the station B is already using the
channel. If these two stations send data at the same time, collisions may occur when both sets
of data arrive at the AP at the same time, resulting in a loss of messages for both stations.
RTS/CTS is designed to prevent collisions due to hidden nodes. An RTS/CTS defines the
biggest size data frame you can send before an RTS (Request To Send)/CTS (Clear to Send)
handshake is invoked.
When a data frame exceeds the RTS/CTS value you set (between 1 to 2432 bytes), the station
that wants to transmit this frame must first send an RTS (Request To Send) message to the AP
for permission to send it. The AP then responds with a CTS (Clear to Send) message to all
other stations within its range to notify them to defer their transmission. It also reserves and
confirms with the requesting station the time frame for the requested transmission.
Stations can send frames smaller than the specified RTS/CTS directly to the AP without the
RTS (Request To Send)/CTS (Clear to Send) handshake.
You should only configure RTS/CTS if the possibility of hidden nodes exists on your network
and the "cost" of resending large frames is more than the extra network overhead involved in
the RTS (Request To Send)/CTS (Clear to Send) handshake.
If the RTS/CTS value is greater than the Fragmentation Threshold value (see next), then the
RTS (Request To Send)/CTS (Clear to Send) handshake will never occur as data frames will
be fragmented before they reach RTS/CTS size.
156
Enabling the RTS Threshold causes redundant network overhead that could
negatively affect the throughput performance instead of providing a remedy.
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Appendix E Wireless LANs
Fragmentation Threshold
A Fragmentation Threshold is the maximum data fragment size (between 256 and 2432
bytes) that can be sent in the wireless network before the AP will fragment the packet into
smaller data frames.
A large Fragmentation Threshold is recommended for networks not prone to interference
while you should set a smaller threshold for busy networks or networks that are prone to
interference.
If the Fragmentation Threshold value is smaller than the RTS/CTS value (see previously)
you set then the RTS (Request To Send)/CTS (Clear to Send) handshake will never occur as
data frames will be fragmented before they reach RTS/CTS size.
Preamble Type
Preamble is used to signal that data is coming to the receiver. Short and Long refer to the
length of the synchronization field in a packet.
Short preamble increases performance as less time sending preamble means more time for
sending data. All IEEE 802.11b/g compliant wireless adapters support long preamble, but not
all support short preamble.
Select Long preamble if you are unsure what preamble mode the wireless adapters support,
and to provide more reliable communications in busy wireless networks.
Select Dynamic to have the AP automatically use short preamble when wireless adapters
support it, otherwise the AP uses long preamble.
The AP and the wireless adapters MUST use the same preamble mode in
order to communicate.
IEEE 802.11g Wireless LAN
IEEE 802.11g is fully compatible with the IEEE 802.11b standard. This means an IEEE
802.11b adapter can interface directly with an IEEE 802.11g access point (and vice versa) at
11 Mbps or lower depending on range. IEEE 802.11g has several intermediate rate steps
between the maximum and minimum data rates. The IEEE 802.11g data rate and modulation
are as follows:
Table 53 IEEE 802.11g
DATA RATE (MBPS)
MODULATION
DBPSK (Differential Binary Phase Shift Keyed)
DQPSK (Differential Quadrature Phase Shift Keying)
5.5 / 11
CCK (Complementary Code Keying)
6/9/12/18/24/36/48/54
OFDM (Orthogonal Frequency Division Multiplexing)
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Appendix E Wireless LANs
Wireless Security Overview
Wireless security is vital to your network to protect wireless communication between wireless
clients, access points and the wired network.
Wireless security methods available on the ZyXEL Device are data encryption, wireless client
authentication, restricting access by device MAC address and hiding the ZyXEL Device
identity.
The following figure shows the relative effectiveness of these wireless security methods
available on your ZyXEL Device.
Table 54 Wireless Security Levels
SECURITY
LEVEL
SECURITY TYPE
Least
Secure
Unique SSID (Default)
Unique SSID with Hide SSID Enabled
MAC Address Filtering
WEP Encryption
IEEE802.1x EAP with RADIUS Server Authentication
Wi-Fi Protected Access (WPA)
Most Secure
WPA2
You must enable the same wireless security settings on the ZyXEL Device and
on all wireless clients that you want to associate with it.
IEEE 802.1x
In June 2001, the IEEE 802.1x standard was designed to extend the features of IEEE 802.11 to
support extended authentication as well as providing additional accounting and control
features. It is supported by Windows XP and a number of network devices. Some advantages
of IEEE 802.1x are:
• User based identification that allows for roaming.
• Support for RADIUS (Remote Authentication Dial In User Service, RFC 2138, 2139) for
centralized user profile and accounting management on a network RADIUS server.
• Support for EAP (Extensible Authentication Protocol, RFC 2486) that allows additional
authentication methods to be deployed with no changes to the access point or the wireless
clients.
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Appendix E Wireless LANs
RADIUS
RADIUS is based on a client-server model that supports authentication, authorization and
accounting. The access point is the client and the server is the RADIUS server. The RADIUS
server handles the following tasks:
• Authentication
Determines the identity of the users.
• Authorization
Determines the network services available to authenticated users once they are connected
to the network.
• Accounting
Keeps track of the client’s network activity.
RADIUS is a simple package exchange in which your AP acts as a message relay between the
wireless client and the network RADIUS server.
Types of RADIUS Messages
The following types of RADIUS messages are exchanged between the access point and the
RADIUS server for user authentication:
• Access-Request
Sent by an access point requesting authentication.
• Access-Reject
Sent by a RADIUS server rejecting access.
• Access-Accept
Sent by a RADIUS server allowing access.
• Access-Challenge
Sent by a RADIUS server requesting more information in order to allow access. The
access point sends a proper response from the user and then sends another Access-Request
message.
The following types of RADIUS messages are exchanged between the access point and the
RADIUS server for user accounting:
• Accounting-Request
Sent by the access point requesting accounting.
• Accounting-Response
Sent by the RADIUS server to indicate that it has started or stopped accounting.
In order to ensure network security, the access point and the RADIUS server use a shared
secret key, which is a password, they both know. The key is not sent over the network. In
addition to the shared key, password information exchanged is also encrypted to protect the
network from unauthorized access.
Types of EAP Authentication
This section discusses some popular authentication types: EAP-MD5, EAP-TLS, EAP-TTLS,
PEAP and LEAP. Your wireless LAN device may not support all authentication types.
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Appendix E Wireless LANs
EAP (Extensible Authentication Protocol) is an authentication protocol that runs on top of the
IEEE 802.1x transport mechanism in order to support multiple types of user authentication. By
using EAP to interact with an EAP-compatible RADIUS server, an access point helps a
wireless station and a RADIUS server perform authentication.
The type of authentication you use depends on the RADIUS server and an intermediary AP(s)
that supports IEEE 802.1x. .
For EAP-TLS authentication type, you must first have a wired connection to the network and
obtain the certificate(s) from a certificate authority (CA). A certificate (also called digital IDs)
can be used to authenticate users and a CA issues certificates and guarantees the identity of
each certificate owner.
EAP-MD5 (Message-Digest Algorithm 5)
MD5 authentication is the simplest one-way authentication method. The authentication server
sends a challenge to the wireless client. The wireless client ‘proves’ that it knows the password
by encrypting the password with the challenge and sends back the information. Password is
not sent in plain text.
However, MD5 authentication has some weaknesses. Since the authentication server needs to
get the plaintext passwords, the passwords must be stored. Thus someone other than the
authentication server may access the password file. In addition, it is possible to impersonate an
authentication server as MD5 authentication method does not perform mutual authentication.
Finally, MD5 authentication method does not support data encryption with dynamic session
key. You must configure WEP encryption keys for data encryption.
EAP-TLS (Transport Layer Security)
With EAP-TLS, digital certifications are needed by both the server and the wireless clients for
mutual authentication. The server presents a certificate to the client. After validating the
identity of the server, the client sends a different certificate to the server. The exchange of
certificates is done in the open before a secured tunnel is created. This makes user identity
vulnerable to passive attacks. A digital certificate is an electronic ID card that authenticates the
sender’s identity. However, to implement EAP-TLS, you need a Certificate Authority (CA) to
handle certificates, which imposes a management overhead.
EAP-TTLS (Tunneled Transport Layer Service)
EAP-TTLS is an extension of the EAP-TLS authentication that uses certificates for only the
server-side authentications to establish a secure connection. Client authentication is then done
by sending username and password through the secure connection, thus client identity is
protected. For client authentication, EAP-TTLS supports EAP methods and legacy
authentication methods such as PAP, CHAP, MS-CHAP and MS-CHAP v2.
PEAP (Protected EAP)
Like EAP-TTLS, server-side certificate authentication is used to establish a secure connection,
then use simple username and password methods through the secured connection to
authenticate the clients, thus hiding client identity. However, PEAP only supports EAP
methods, such as EAP-MD5, EAP-MSCHAPv2 and EAP-GTC (EAP-Generic Token Card),
for client authentication. EAP-GTC is implemented only by Cisco.
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Appendix E Wireless LANs
LEAP
LEAP (Lightweight Extensible Authentication Protocol) is a Cisco implementation of IEEE
802.1x.
Dynamic WEP Key Exchange
The AP maps a unique key that is generated with the RADIUS server. This key expires when
the wireless connection times out, disconnects or reauthentication times out. A new WEP key
is generated each time reauthentication is performed.
If this feature is enabled, it is not necessary to configure a default encryption key in the
Wireless screen. You may still configure and store keys here, but they will not be used while
Dynamic WEP is enabled.
EAP-MD5 cannot be used with Dynamic WEP Key Exchange
For added security, certificate-based authentications (EAP-TLS, EAP-TTLS and PEAP) use
dynamic keys for data encryption. They are often deployed in corporate environments, but for
public deployment, a simple user name and password pair is more practical. The following
table is a comparison of the features of authentication types.
Table 55 Comparison of EAP Authentication Types
EAP-MD5
EAP-TLS
EAP-TTLS
PEAP
LEAP
Mutual Authentication
No
Yes
Yes
Yes
Yes
Certificate – Client
No
Yes
Optional
Optional
No
Certificate – Server
No
Yes
Yes
Yes
No
Dynamic Key Exchange
No
Yes
Yes
Yes
Yes
Credential Integrity
None
Strong
Strong
Strong
Moderate
Deployment Difficulty
Easy
Hard
Moderate
Moderate
Moderate
Client Identity Protection
No
No
Yes
Yes
No
WPA and WPA2
Wi-Fi Protected Access (WPA) is a subset of the IEEE 802.11i standard. WPA2 (IEEE
802.11i) is a wireless security standard that defines stronger encryption, authentication and
key management than WPA.
Key differences between WPA or WPA2 and WEP are improved data encryption and user
authentication.
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Appendix E Wireless LANs
If both an AP and the wireless clients support WPA2 and you have an external RADIUS
server, use WPA2 for stronger data encryption. If you don't have an external RADIUS server,
you should use WPA2-PSK (WPA2-Pre-Shared Key) that only requires a single (identical)
password entered into each access point, wireless gateway and wireless client. As long as the
passwords match, a wireless client will be granted access to a WLAN.
If the AP or the wireless clients do not support WPA2, just use WPA or WPA-PSK depending
on whether you have an external RADIUS server or not.
Select WEP only when the AP and/or wireless clients do not support WPA or WPA2. WEP is
less secure than WPA or WPA2.
Encryption
Both WPA and WPA2 improve data encryption by using Temporal Key Integrity Protocol
(TKIP), Message Integrity Check (MIC) and IEEE 802.1x. WPA and WPA2 use Advanced
Encryption Standard (AES) in the Counter mode with Cipher block chaining Message
authentication code Protocol (CCMP) to offer stronger encryption than TKIP.
TKIP uses 128-bit keys that are dynamically generated and distributed by the authentication
server. AES (Advanced Encryption Standard) is a block cipher that uses a 256-bit
mathematical algorithm called Rijndael. They both include a per-packet key mixing function,
a Message Integrity Check (MIC) named Michael, an extended initialization vector (IV) with
sequencing rules, and a re-keying mechanism.
WPA and WPA2 regularly change and rotate the encryption keys so that the same encryption
key is never used twice.
The RADIUS server distributes a Pairwise Master Key (PMK) key to the AP that then sets up
a key hierarchy and management system, using the PMK to dynamically generate unique data
encryption keys to encrypt every data packet that is wirelessly communicated between the AP
and the wireless clients. This all happens in the background automatically.
The Message Integrity Check (MIC) is designed to prevent an attacker from capturing data
packets, altering them and resending them. The MIC provides a strong mathematical function
in which the receiver and the transmitter each compute and then compare the MIC. If they do
not match, it is assumed that the data has been tampered with and the packet is dropped.
By generating unique data encryption keys for every data packet and by creating an integrity
checking mechanism (MIC), with TKIP and AES it is more difficult to decrypt data on a Wi-Fi
network than WEP and difficult for an intruder to break into the network.
The encryption mechanisms used for WPA(2) and WPA(2)-PSK are the same. The only
difference between the two is that WPA(2)-PSK uses a simple common password, instead of
user-specific credentials. The common-password approach makes WPA(2)-PSK susceptible to
brute-force password-guessing attacks but it’s still an improvement over WEP as it employs a
consistent, single, alphanumeric password to derive a PMK which is used to generate unique
temporal encryption keys. This prevent all wireless devices sharing the same encryption keys.
(a weakness of WEP)
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Appendix E Wireless LANs
User Authentication
WPA and WPA2 apply IEEE 802.1x and Extensible Authentication Protocol (EAP) to
authenticate wireless clients using an external RADIUS database. WPA2 reduces the number
of key exchange messages from six to four (CCMP 4-way handshake) and shortens the time
required to connect to a network. Other WPA2 authentication features that are different from
WPA include key caching and pre-authentication. These two features are optional and may not
be supported in all wireless devices.
Key caching allows a wireless client to store the PMK it derived through a successful
authentication with an AP. The wireless client uses the PMK when it tries to connect to the
same AP and does not need to go with the authentication process again.
Pre-authentication enables fast roaming by allowing the wireless client (already connecting to
an AP) to perform IEEE 802.1x authentication with another AP before connecting to it.
Wireless Client WPA Supplicants
A wireless client supplicant is the software that runs on an operating system instructing the
wireless client how to use WPA. At the time of writing, the most widely available supplicant is
the WPA patch for Windows XP, Funk Software's Odyssey client.
The Windows XP patch is a free download that adds WPA capability to Windows XP's builtin "Zero Configuration" wireless client. However, you must run Windows XP to use it.
WPA(2) with RADIUS Application Example
You need the IP address of the RADIUS server, its port number (default is 1812), and the
RADIUS shared secret. A WPA(2) application example with an external RADIUS server
looks as follows. "A" is the RADIUS server. "DS" is the distribution system.
1 The AP passes the wireless client's authentication request to the RADIUS server.
2 The RADIUS server then checks the user's identification against its database and grants
or denies network access accordingly.
3 The RADIUS server distributes a Pairwise Master Key (PMK) key to the AP that then
sets up a key hierarchy and management system, using the pair-wise key to dynamically
generate unique data encryption keys to encrypt every data packet that is wirelessly
communicated between the AP and the wireless clients.
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Appendix E Wireless LANs
Figure 90 WPA(2) with RADIUS Application Example
WPA(2)-PSK Application Example
A WPA(2)-PSK application looks as follows.
1 First enter identical passwords into the AP and all wireless clients. The Pre-Shared Key
(PSK) must consist of between 8 and 63 ASCII characters or 64 hexadecimal characters
(including spaces and symbols).
2 The AP checks each wireless client's password and (only) allows it to join the network if
the password matches.
3 The AP and wireless clients use the pre-shared key to generate a common PMK
(Pairwise Master Key).
4 The AP and wireless clients use the TKIP or AES encryption process to encrypt data
exchanged between them.
Figure 91 WPA(2)-PSK Authentication
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Appendix E Wireless LANs
Security Parameters Summary
Refer to this table to see what other security parameters you should configure for each
Authentication Method/ key management protocol type. MAC address filters are not
dependent on how you configure these security features.
Table 56 Wireless Security Relational Matrix
AUTHENTICATION
ENCRYPTIO
METHOD/ KEY
MANAGEMENT PROTOCOL N METHOD
ENTER
MANUAL KEY
IEEE 802.1X
Open
No
Disable
None
Enable without Dynamic WEP Key
Open
Shared
WEP
WEP
No
Enable with Dynamic WEP Key
Yes
Enable without Dynamic WEP Key
Yes
Disable
No
Enable with Dynamic WEP Key
Yes
Enable without Dynamic WEP Key
Yes
Disable
WPA
TKIP/AES
No
Enable
WPA-PSK
TKIP/AES
Yes
Disable
WPA2
TKIP/AES
No
Enable
WPA2-PSK
TKIP/AES
Yes
Disable
Antenna Overview
An antenna couples RF signals onto air. A transmitter within a wireless device sends an RF
signal to the antenna, which propagates the signal through the air. The antenna also operates in
reverse by capturing RF signals from the air.
Positioning the antennas properly increases the range and coverage area of a wireless LAN.
Antenna Characteristics
Frequency
An antenna in the frequency of 2.4GHz (IEEE 802.11b) or 5GHz(IEEE 802.11a) is needed to
communicate efficiently in a wireless LAN.
Radiation Pattern
A radiation pattern is a diagram that allows you to visualize the shape of the antenna’s
coverage area.
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Appendix E Wireless LANs
Antenna Gain
Antenna gain, measured in dB (decibel), is the increase in coverage within the RF beam width.
Higher antenna gain improves the range of the signal for better communications.
For an indoor site, each 1 dB increase in antenna gain results in a range increase of
approximately 2.5%. For an unobstructed outdoor site, each 1dB increase in gain results in a
range increase of approximately 5%. Actual results may vary depending on the network
environment.
Antenna gain is sometimes specified in dBi, which is how much the antenna increases the
signal power compared to using an isotropic antenna. An isotropic antenna is a theoretical
perfect antenna that sends out radio signals equally well in all directions. dBi represents the
true gain that the antenna provides.
Types of Antennas for WLAN
There are two types of antennas used for wireless LAN applications.
• Omni-directional antennas send the RF signal out in all directions on a horizontal plane.
The coverage area is torus-shaped (like a donut) which makes these antennas ideal for a
room environment. With a wide coverage area, it is possible to make circular overlapping
coverage areas with multiple access points.
• Directional antennas concentrate the RF signal in a beam, like a flashlight does with the
light from its bulb. The angle of the beam determines the width of the coverage pattern.
Angles typically range from 20 degrees (very directional) to 120 degrees (less directional).
Directional antennas are ideal for hallways and outdoor point-to-point applications.
Positioning Antennas
In general, antennas should be mounted as high as practically possible and free of
obstructions. In point-to–point application, position both antennas at the same height and in a
direct line of sight to each other to attain the best performance.
For omni-directional antennas mounted on a table, desk, and so on, point the antenna up. For
omni-directional antennas mounted on a wall or ceiling, point the antenna down. For a single
AP application, place omni-directional antennas as close to the center of the coverage area as
possible.
For directional antennas, point the antenna in the direction of the desired coverage area.
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APPENDIX
Pop-up Windows, JavaScripts
and Java Permissions
In order to use the web configurator you need to allow:
• Web browser pop-up windows from your device.
• JavaScripts (enabled by default).
• Java permissions (enabled by default).
Internet Explorer 6 screens are used here. Screens for other Internet Explorer
versions may vary.
Internet Explorer Pop-up Blockers
You may have to disable pop-up blocking to log into your device.
Either disable pop-up blocking (enabled by default in Windows XP SP (Service Pack) 2) or
allow pop-up blocking and create an exception for your device’s IP address.
Disable pop-up Blockers
1 In Internet Explorer, select Tools, Pop-up Blocker and then select Turn Off Pop-up
Blocker.
Figure 92 Pop-up Blocker
You can also check if pop-up blocking is disabled in the Pop-up Blocker section in the
Privacy tab.
1 In Internet Explorer, select Tools, Internet Options, Privacy.
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Appendix F Pop-up Windows, JavaScripts and Java Permissions
2 Clear the Block pop-ups check box in the Pop-up Blocker section of the screen. This
disables any web pop-up blockers you may have enabled.
Figure 93 Internet Options: Privacy
3 Click Apply to save this setting.
Enable pop-up Blockers with Exceptions
Alternatively, if you only want to allow pop-up windows from your device, see the following
steps.
1 In Internet Explorer, select Tools, Internet Options and then the Privacy tab.
2 Select Settings…to open the Pop-up Blocker Settings screen.
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Appendix F Pop-up Windows, JavaScripts and Java Permissions
Figure 94 Internet Options: Privacy
3 Type the IP address of your device (the web page that you do not want to have blocked)
with the prefix “http://”. For example, http://192.168.167.1.
4 Click Add to move the IP address to the list of Allowed sites.
Figure 95 Pop-up Blocker Settings
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Appendix F Pop-up Windows, JavaScripts and Java Permissions
5 Click Close to return to the Privacy screen.
6 Click Apply to save this setting.
JavaScripts
If pages of the web configurator do not display properly in Internet Explorer, check that
JavaScripts are allowed.
1 In Internet Explorer, click Tools, Internet Options and then the Security tab.
Figure 96 Internet Options: Security
170
Click the Custom Level... button.
Scroll down to Scripting.
Under Active scripting make sure that Enable is selected (the default).
Under Scripting of Java applets make sure that Enable is selected (the default).
Click OK to close the window.
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Appendix F Pop-up Windows, JavaScripts and Java Permissions
Figure 97 Security Settings - Java Scripting
Java Permissions
From Internet Explorer, click Tools, Internet Options and then the Security tab.
Click the Custom Level... button.
Scroll down to Microsoft VM.
Under Java permissions make sure that a safety level is selected.
Click OK to close the window.
Figure 98 Security Settings - Java
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Appendix F Pop-up Windows, JavaScripts and Java Permissions
JAVA (Sun)
1 From Internet Explorer, click Tools, Internet Options and then the Advanced tab.
2 Make sure that Use Java 2 for
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