Cisco IOS Software Configuration Guide for Cisco Aironet Access Points, 12.2(13)JA
Configuring Repeater and Standby Access Points
Downloads: This chapterpdf (PDF - 266.0KB) The complete bookPDF (PDF - 5.8MB) | Feedback

Configuring Repeater and Standby Access Points

Table Of Contents

Configuring Repeater and Standby Access Points

Understanding Repeater Access Points

Configuring a Repeater Access Point

Default Configuration

Guidelines for Repeaters

Setting Up a Repeater

Verifying Repeater Operation

Setting Up a Repeater As a LEAP Client

Setting Up a Repeater As a WPA Client

Understanding Hot Standby

Configuring a Hot Standby Access Point

Verifying Standby Operation


Configuring Repeater and Standby Access Points


This chapter descibes how to configure your access point as a hot standby unit or as a repeater unit. This chapter contains these sections:

Understanding Repeater Access Points

Configuring a Repeater Access Point

Understanding Hot Standby

Configuring a Hot Standby Access Point

Understanding Repeater Access Points

A repeater access point is not connected to the wired LAN; it is placed within radio range of an access point connected to the wired LAN to extend the range of your infrastructure or to overcome an obstacle that blocks radio communication. You can configure either the 2.4-GHz radio or the 5-GHz radio as a repeater. In access points with two radios, only one radio can be a repeater; the other radio must be configured as a root radio.

The repeater forwards traffic between wireless users and the wired LAN by sending packets to either another repeater or to an access point connected to the wired LAN. The data is sent through the route that provides the best performance for the client. When you configure an access point as a repeater, the access point's Ethernet port does not forward traffic.

You can set up a chain of several repeater access points, but throughput for client devices at the end of the repeater chain will be quite low. Because each repeater must receive and then re-transmit each packet on the same channel, throughput is cut in half for each repeater you add to the chain.

A repeater access point associates to the access point with which it has the best connectivity. However, you can specify the access point to which the repeater associates. Setting up a static, specific association between a repeater and a root access point improves repeater performance.

To set up repeaters, you must enable Aironet extensions on both the parent (root) access point and the repeater access points. Aironet extensions, which are enabled by default, improve the access point's ability to understand the capabilities of Cisco Aironet client devices associated with the access point. Disabling Aironet extensions sometimes improves the interoperability between the access point and non-Cisco client devices. Non-Cisco client devices might have difficulty communicating with repeater access points and the root access point to which repeaters are associated.


Note Because access points create a virtual interface for each radio interface, repeater access points associate to the root access point twice: once for the actual interface and once for the virtual interface.


Figure 19-1 shows an access point acting as a repeater.

Figure 19-1 Access Point as a Repeater

Configuring a Repeater Access Point

This section provides instructions for setting up an access point as a repeater and includes these sections:

Default Configuration

Guidelines for Repeaters

Setting Up a Repeater

Verifying Repeater Operation

Setting Up a Repeater As a LEAP Client

Setting Up a Repeater As a WPA Client

Default Configuration

Access points are configured as root units by default. Table 19-1 shows the default values for settings that control the access point's role in the wireless LAN.

Table 19-1 Default Settings for Role in Wireless LAN

Feature
Default Setting

Station role

Root

Parent

none

Extensions

Aironet


Guidelines for Repeaters

Follow these guidelines when configuring repeater access points:

Use repeaters to serve client devices that do not require high throughput. Repeaters extend the coverage area of your wireless LAN, but they drastically reduce throughput.

Use repeaters when most if not all client devices that associate with the repeaters are Cisco Aironet clients. Non-Cisco client devices sometimes have trouble communicating with repeater access points.

Make sure that the data rates configured on the repeater access point match the data rates on the parent access point. For instructions on configuring data rates, see the "Configuring Radio Data Rates" section.


Note Repeater access points running Cisco IOS software cannot associate to parent access points that that do not run Cisco IOS software.



Note Repeater access points do not support wireless domain services (WDS). Do not configure a repeater access point as a WDS candidate, and do not configure a WDS access point to fall back to repeater mode in case of Ethernet failure.


Setting Up a Repeater

Beginning in Privileged Exec mode, follow these steps to configure an access point as a repeater:

 
Command
Purpose

Step 1 

configure terminal

Enter global configuration mode.

Step 2 

interface dot11radio { 0 | 1 }

Enter interface configuration mode for the radio interface. The 2.4-GHz radio is radio 0, and the 5-GHz radio is radio 1.

Step 3 

ssid ssid-string

Create the SSID that the repeater uses to associate to a root access point; in the next step designate this SSID as an infrastructure SSID. If you created an infrastructure SSID on the root access point, create the same SSID on the repeater, also.

Step 4 

infrastructure-ssid [optional]

Designate the SSID as an infrastructure SSID. The repeater uses this SSID to associate to the root access point. Infrastructure devices must associate to the repeater access point using this SSID unless you also enter the optional keyword.

Step 5 

exit

Exit SSID configuration mode and return to radio interface configuration mode.

Step 6 

station-role repeater

Set the access point's role in the wireless LAN to repeater.

Step 7 

dot11 extensions aironet

If Aironet extensions are disabled, enable Aironet extensions.

Step 8 

parent {1-4} mac-address [timeout]

(Optional) Enter the MAC address for the access point to which the repeater should associate.

You can enter MAC addresses for up to four parent access points. The repeater attempts to associate to MAC address 1 first; if that access point does not respond, the repeater tries the next access point in its parent list.

(Optional) You can also enter a timeout value in seconds that determines how long the repeater attempts to associate to a parent access point before trying the next parent in the list. Enter a timeout value from 0 to 65535 seconds.

Step 9 

end

Return to privileged EXEC mode.

Step 10 

copy running-config startup-config

(Optional) Save your entries in the configuration file.

This example shows how to set up a repeater acess point with three potential parents:

AP# configure terminal
AP(config)# interface dot11radio 0
AP(config-if)# ssid chicago
AP(config-ssid)# infrastructure-ssid
AP(config-ssid)# exit
AP(config-if)# station-role repeater
AP(config-if)# dot11 extensions aironet
AP(config-if)# parent 1 0987.1234.h345 900
AP(config-if)# parent 2 7809.b123.c345 900
AP(config-if)# parent 3 6543.a456.7421 900
AP(config-if)# end

Verifying Repeater Operation

After you set up the repeater, check the LEDs on top of the repeater access point. If your repeater is functioning correctly, the LEDs on the repeater and the root access point to which it is associated behave like this:

The status LED on the root access point is steady green, indicating that at least one client device is associated with it (in this case, the repeater).

The status LED on the repeater access point is steady green when it is associated with the root access point and the repeater has client devices associated to it. The repeater's status LED flashes (steady green for 7/8 of a second and off for 1/8 of a second) when it is associated with the root access point but the repeater has no client devices associated to it.

The repeater access point should also appear as associated with the root access point in the root access point's Association Table.

Setting Up a Repeater As a LEAP Client

You can set up a repeater access point to authenticate to your network like other wireless client devices. After you provide a network username and password for the repeater access point, it authenticates to your network using LEAP, Cisco's wireless authentication method, and receives and uses dynamic WEP keys.

Setting up a repeater as a LEAP client requires three major steps:

1. Create an authentication username and password for the repeater on your authentication server.

2. Configure LEAP authentication on the root access point to which the repeater associates. The access point to which the repeater associates is called the parent access point. See "Configuring Authentication Types," for instructions on setting up authentication.


Note On the repeater access point, you must enable the same cipher suite or WEP encryption method and WEP features that are enabled on the parent access point.


3. Configure the repeater to act as a LEAP client. Beginning in Privileged Exec mode, follow these instructions to set up the repeater as a LEAP client:

 
Command
Purpose

Step 1 

configure terminal

Enter global configuration mode.

Step 2 

interface dot11radio { 0 | 1 }

Enter interface configuration mode for the radio interface. The 2.4-GHz radio is radio 0, and the 5-GHz radio is radio 1.

Step 3 

ssid ssid-string

Create an SSID and enter SSID configuration mode for the new SSID. The SSID can consist of up to 32 alphanumeric characters, but they should not include spaces. SSIDs are case-sensitive.

Step 4 

authentication network-eap list-name

Enable LEAP authentication on the repeater so that LEAP-enabled client devices can authenticate through the repeater. For list-name, specify the list name you want to use for EAP authentication. You define list names for EAP and for MAC addresses using the aaa authentication login command. These lists define the authentication methods activated when a user logs in and indirectly identify the location where the authentication information is stored.

Step 5 

authentication client username username
password password

Configure the username and password that the repeater uses when it performs LEAP authentication. This username and password must match the username and password that you set up for the repeater on the authentication server.

Step 6 

infrastructure ssid [optional]

(Optional) Designate the SSID as the SSID that other access points and workgroup bridges use to associate to this access point. If you do not designate an SSID as the infrastructure SSID, infrastructure devices can associate to the access point using any SSID. If you designate an SSID as the infrastructure SSID, infrastructure devices must associate to the access point using that SSID unless you also enter the optional keyword.

Step 7 

end

Return to privileged EXEC mode.

Step 8 

copy running-config startup-config

(Optional) Save your entries in the configuration file.

Setting Up a Repeater As a WPA Client

WPA key management uses a combination of encryption methods to protect communication between client devices and the access point. You can set up a repeater access point to authenticate to your network like other WPA-enabled client devices.

Beginning in Privileged Exec mode, follow these steps to set up the repeater as a WPA client:

 
Command
Purpose

Step 1 

configure terminal

Enter global configuration mode.

Step 2 

interface dot11radio { 0 | 1 }

Enter interface configuration mode for the radio interface. The 2.4-GHz radio is radio 0, and the 5-GHz radio is radio 1.

Step 3 

ssid ssid-string

Create an SSID and enter SSID configuration mode for the new SSID. The SSID can consist of up to 32 alphanumeric characters. SSIDs are case sensitive.

Step 4 

authentication open

Enable open authentication for the SSID.

Step 5 

authentication key-management wpa

Enable WPA authenticated key management for the SSID.

Step 6 

infrastructure ssid

Designate the SSID as the SSID that the repeater uses to associate to other access points.

Step 7 

wpa-psk { hex | ascii } [ 0 | 7 ] encryption-key

Enter a pre-shared key for the repeater.

Enter the key using either hexadecimal or ASCII characters. If you use hexadecimal, you must enter 64 hexadecimal characters to complete the 256-bit key. If you use ASCII, you must enter from 8 to 63 ASCII characters, and the access point expands the key for you.

Step 8 

end

Return to privileged EXEC mode.

Step 9 

copy running-config startup-config

(Optional) Save your entries in the configuration file.

Understanding Hot Standby

Hot Standby mode designates an access point as a backup for another access point. The standby access point is placed near the access point it monitors, configured exactly the same as the monitored access point. The standby access point associates with the monitored access point as a client and sends IAPP queries to the monitored access point through both the Ethernet and the radio ports. If the monitored access point fails to respond, the standby access point comes online and takes the monitored access point's place in the network.

Except for the IP address, the standby access point's settings should be identical to the settings on the monitored access point. If the monitored access point goes offline and the standby access point takes its place in the network, matching settings ensures that client devices can switch easily to the standby access point.

The standby access point monitors another access point in a device-to-device relationship, not in an interface-to-interface relationship. For example, you cannot configure the standby access point's 5-GHz radio to monitor the 5-GHz radio in access point alpha and the standby's 2.4-GHz radio to monitor the 2.4-GHz radio in access point bravo. You also cannot configure one radio in a dual-radio access point as a standby radio and configure the other radio to serve client devices.

Hot standby mode is disabled by default.


Note If the monitored access point malfunctions and the standby access point takes its place, repeat the hot standby setup on the standby access point when you repair or replace the monitored access point. The standby access point does not revert to standby mode automatically.


Configuring a Hot Standby Access Point

When you set up the standby access point, you must enter the MAC address of the access point that the standby unit will monitor. Record the MAC address of the monitored access point before you configure the standby access point.

The standby access point also must duplicate several key settings on the monitored access point. These settings are:

Primary SSID (as well as additional SSIDs configured on the monitored access point)

Default IP Subnet Mask

Default Gateway

Data rates

WEP settings

Authentication types and authentication servers

Check the monitored access point and record these settings before you set up the standby access point.


Note Wireless client devices associated to the standby access point lose their connections during the hot standby setup process.



Tip To quickly duplicate the monitored access point's settings on the standby access point, save the monitored access point configuration and load it on the standby access point. See the "Working with Configuration Files" section for instructions on uploading and downloading configuration files.


Beginning in Privileged Exec mode, follow these steps to enable hot standby mode on an access point:

 
Command
Purpose

Step 1 

configure terminal

Enter global configuration mode.

Step 2 

iapp standby mac-address

Puts the access point into standby mode and specifies the MAC address of radio on the monitored access point.

Note When you configure a 1200 Series access point with two radios to monitor a 1200 Series access point with two radios, you must enter the MAC addresses of both the monitored 2.4-GHz and 5-GHz radios. Enter the 2.4-GHz radio MAC address first, followed by the 5-GHz radio MAC address.

Step 3 

interface dot11radio { 0 | 1 }

Enter interface configuration mode for the radio interface. The 2.4-GHz radio is radio 0, and the 5-GHz radio is radio 1.

Step 4 

ssid ssid-string

Create the SSID that the standby access point uses to associate to the monitored access point; in the next step designate this SSID as an infrastructure SSID. If you created an infrastructure SSID on the monitored access point, create the same SSID on the standby access point, also.

Step 5 

infrastructure-ssid [optional]

Designate the SSID as an infrastructure SSID. The standby uses this SSID to associate to the monitored access point. If the standby access point takes the place of the monitored access point, infrastructure devices must associate to the standby access point using this SSID unless you also enter the optional keyword.

Step 6 

authentication client username username
password password

If the monitored access point is configured to require LEAP authentication, configure the username and password that the standby access point uses when it performs LEAP authentication. This username and password must match the username and password that you set up for the standby access point on the authentication server.

Step 7 

exit

Exit SSID configuration mode and return to radio interface configuration mode.

Step 8 

iapp standby poll-frequency seconds

Sets the number of seconds between queries that the standby access point sends to the monitored access point's radio and Ethernet ports. The default poll frequency is 2 seconds.

Step 9 

iapp standby timeout seconds

Sets the number of seconds the standby access point waits for a response from the monitored access point before it assumes that the monitored access point has malfunctioned. The default timeout is 20 seconds.

Step 10 

show iapp standby-parms

Verify your entries. If the access point is in standby mode, this command displays the standby parameters, including the MAC address of the monitored access point and the poll-frequency and timeout values. If the access point is not in standby mode, no iapp standby mac-address appears.

Step 11 

end

Return to privileged EXEC mode.

Step 12 

copy running-config startup-config

(Optional) Save your entries in the configuration file.

After you enable standby mode, configure the settings that you recorded from the monitored access point to match on the standby access point.

Verifying Standby Operation

Use this command to check the status of the standby access point:

show iapp standby-status

This command displays the status of the standby access point. Table 19-2 lists the standby status messages that can appear.

Table 19-2 Standby Status Messages 

Message
Description

IAPP Standby is Disabled

The access point is not configured for standby mode.

IAPP—AP is in standby mode

The access point is in standby mode.

IAPP—AP is operating in active mode

The standby access point has taken over for the monitored access point and is functioning as a root access point.

IAPP—AP is operating in repeater mode

The standby access point has taken over for the monitored access point and is functioning as a repeater access point.

Standby status: Initializing

The standby access point is initializing link tests with the monitored access point.

Standby status: Takeover

The standby access point has transitioned to active mode.

Standby status: Stopped

Standby mode has been stopped by a configuration command.

Standby status: Ethernet Linktest Failed

An Ethernet link test failed from the standby access point to the monitored access point.

Standby status: Radio Linktest Failed

A radio link test failed from the standby access point to the monitored access point.

Standby status: Standby Error

An undefined error occurred.

Standby State: Init

The standby access point is initializing link tests with the monitored access point.

Standby State: Running

The standby access point is operating in standby mode and is running link tests to the monitored access point.

Standby State: Stopped

Standby mode has been stopped by a configuration command.

Standby State: Not Running

The access point is not in standby mode.


Use this command to check the standby configuration:

show iapp standby-parms

This command displays the MAC address of the standby access point, the standby timeout, and the poll-frequency values. If no standby access point is configured, this message appears:

no iapp standby mac-address

If a standby access point takes over for the monitored access point, you can use the show iapp statistics command to help determine the reason that the standby access point took over.