Configuring Repeater and Standby Access Points

C H A P T E R
19
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, page 19-2
•
Configuring a Repeater Access Point, page 19-3
•
Understanding Hot Standby, page 19-8
•
Configuring a Hot Standby Access Point, page 19-8
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Understanding Repeater Access Points
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.
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Configuring Repeater and Standby Access Points
Configuring a Repeater Access Point
Figure 19-1 Access Point as a Repeater
Access Point
(Root Unit)
Wired LAN
66000
Access Point
(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, page 19-4
•
Guidelines for Repeaters, page 19-4
•
Setting Up a Repeater, page 19-4
•
Verifying Repeater Operation, page 19-5
•
Setting Up a Repeater As a LEAP Client, page 19-6
•
Setting Up a Repeater As a WPA Client, page 19-7
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Configuring a Repeater Access Point
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 on page 6-4.
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.
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Configuring a Repeater Access Point
Command
Purpose
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.
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Configuring a Repeater Access Point
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 Chapter 10, “Configuring
Authentication Types,” for instructions on setting up authentication.
Note
3.
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.
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.
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Configuring a Repeater Access Point
Command
Purpose
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 Enable WPA authenticated key management for the SSID.
wpa
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.
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Understanding Hot Standby
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.
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Configuring a Hot Standby Access Point
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 on page 20-8 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.
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Configuring a Hot Standby Access Point
Command
Purpose
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.
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Configuring a Hot Standby Access Point
Table 19-2 Standby Status Messages (continued)
Message
Description
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.
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