An unresponsive AAA server introduces a delay in the processing of AAA requests. An MDS switch can periodically monitor an AAA server to check whether it is responding (or alive) to save time in processing AAA requests. The switch marks unresponsive AAA servers as dead and does not send AAA requests to any dead AAA servers. The switch periodically monitors dead AAA servers and brings them to the alive state when they respond. This monitoring process verifies that an AAA server is in a working state before real AAA requests are sent its way. Whenever an AAA server changes to the dead or alive state, an SNMP trap is 897generated, and the MDS switch warns the administrator that a failure is taking place before it can impact performance.
Figure 20-1 depicts AAA server states.
Figure 20-1 AAA Server States
The monitoring interval for alive servers and dead servers is different and can be configured by the user. AAA server monitoring is performed by sending a test authentication request to the AAA server.
The AAA server monitoring parameters can be configured globally for all servers or individually for a specific server. The global configurations will apply to all servers that do not have individual monitoring parameters defined. For any server, the individual test parameter defined for that particular server will always get precedence over the global settings.