The AAA Dead-Server Detection feature allows you to determine the criteria that are used to mark a RADIUS server as dead.
That is, you can configure the minimum amount of time, in seconds, that must elapse from the time that the router last received
a valid packet from the RADIUS server to the time the server is marked as dead. If a packet has not been received since the
router booted, and there is a timeout, the time criterion will be treated as though it has been met.
In addition, you can configure the number of consecutive timeouts that must occur on the router before the RADIUS server is
marked as dead. If the server performs both authentication and accounting, both types of packets are included in the number.
Improperly constructed packets are counted as though they are timeouts. Only retransmissions are counted, not the initial
transmission. (Each timeout causes one retransmission to be sent.)
Both the time criterion and the tries criterion must be met for the server to be marked as dead.
The RADIUS dead-server detection configuration will result in the prompt detection of RADIUS servers that have stopped responding.
This configuration will also result in the avoidance of servers being improperly marked as dead when they are “swamped” (responding
slowly) and the avoidance of the state of servers being rapidly changed from dead to live to dead again. This prompt detection
of nonresponding RADIUS servers and the avoidance of swamped and dead-to-live-to-dead-again servers will result in less deadtime
and quicker packet processing.