Setting SNMP Timeout Values

Problem

You want to adjust the SNMP trap timeout value.

Solution

You can use the following configuration command to adjust a router's SNMP trap timeout value:

Router#configure terminal Enter configuration commands, one per line. End with CNTL/Z. Router(config)#snmp-server trap-timeout 60 Router(config)#end Router#

To adjust a router's SNMP inform timeout value, use the follow configuration commands:

Router#configure terminal Enter configuration commands, one per line. End with CNTL/Z. Router(config)#snmp-server inform timeout 120 Router(config)#end Router#

Discussion

Before a router can send an SNMP trap, it must have a route to the destination address of the trap. If a route to the SNMP server does not exist, the router will store the trap in the retransmission queue. By default, the router will hold a trap in the retransmission queue for 30 seconds before attempting to deliver it again. Sometimes it is useful to modify the default wait time to improve the chances of successful delivery.

For instance, if the router has to send the trap over a low-speed dial backup interface, 30 seconds may not be enough time for it to trigger a call, establish connectivity, and stabilize a routing table. In a situation like this, you should consider increasing the trap timeout. The value is specified as an integer number of seconds between 1 and 1,000.

SNMP informs use timeouts differently. The inform timeout is the number of seconds that the router waits for an acknowledgement before resending. The default value is 30 seconds, but the router will accept any value between 0 and 4,294,967,295 seconds.

Note that increasing the timeout values for traps and informs means that the router will tend to hold these messages for longer. And this, in turn, generally means that you will have to increase the queue size in order to hold them.