Identifying The Radius Server Host - Cisco Catalyst 4500 Series Software Configuration Manual

Chapter 49 Configuring 802.1X Port-Based Authentication

Identifying the RADIUS Server Host

Switch-to-RADIUS-server communication involves several components:
Hostname or IP address
•
Authentication destination port
•
Accounting destination port
•
• Key string
• Timeout period
• Retransmission value
You identify RADIUS security servers by their hostname or IP address, hostname 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 failover backup to the first one. Using this example, if the first host entry fails to provide
accounting services, the
%RADIUS-4-RADIUS_DEAD
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-server timeout, radius-server
retransmit, and radius-server key. To apply these values on a specific RADIUS server, use the radius-server host global
configuration command.
If you configure both global and per-server functions (timeout, retransmission, and key commands) on
Note
the switch, the per-server timer, retransmission, and key value commands override global timer,
retransmission, and key value commands. For information on configuring these settings on all RADIUS
servers, see the
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" section on page
message appears, and then the switch tries the second host entry configured
"Configuring Settings for All RADIUS Servers" section on page
Catalyst 4500 Series Switch, Cisco IOS Software Configuration Guide - Cisco IOS XE 3.9.xE and IOS 15.2(5)Ex
49-107.
Controlling Switch Access with RADIUS
49-110.
49-103