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Catalyst 2950 Desktop Switch Software Configuration Guide
78-11380-03
Chapter 6 Configuring the System
Controlling Switch Access with RADIUS
Identifying the RADIUS Server Host
Switch-to-RADIUS-server communication involves several components:
• Host name or IP address
• Authentication destination port
• Accounting destination port
• Key string
• Timeout period
• Retransmission value
You identify RADIUS security servers by their host name or IP address, host name and specific UDP
port numbers, or their IP address and specific UDP port numbers. The combination of the IP address and
the UDP port number creates a unique identifier, allowing different ports to be individually defined as
RADIUS hosts providing a specific AAA service. This unique identifier enables RADIUS requests to be
sent to multiple UDP ports on a server at the same IP address.
If two different host entries on the same RADIUS server are configured for the same service—for
example, accounting—the second host entry configured acts as a fail-over backup to the first one. Using
this example, if the first host entry fails to provide accounting services, the switch tries the second host
entry configured on the same device for accounting services. (The RADIUS host entries are tried in the
order that they are configured.)
A RADIUS server and the switch use a shared secret text string to encrypt passwords and exchange
responses. To configure RADIUS to use the AAA security commands, you must specify the host running
the RADIUS server daemon and a secret text (key) string that it shares with the switch.
The timeout, retransmission, and encryption key values can be configured globally for all RADIUS
servers, on a per-server basis, or in some combination of global and per-server settings. To apply these
settings globally to all RADIUS servers communicating with the switch, use the three unique global
configuration commands: radius-servertimeout, radius-server retransmit,andradius-server key.To
apply these values on a specific RADIUS server, use the radius-server host global configuration
command.
Note If you configure both global and per-server functions (timeout, retransmission, and key
commands) on the switch, the per-server timer, retransmission, and key value commands
override global timer, retransmission, and key value commands. For information on
configuring these setting on all RADIUS servers, see the “Configuring Settings for All
RADIUS Servers” sectiononpage6-35.
You can configure the switch to use AAA server groups to group existing server hosts for authentication.
For more information, see the “Defining AAA Server Groups” sectiononpage6-31.
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