Understanding RIP Timers
RIP uses several timers to regulate its operation.
The update interval is the interval at which routes that are learned by RIP are advertised to neighbors. This timer controls the interval between routing updates. The update interval is set to 30 seconds, by default, with a small random amount of time added when the timer is reset. This added time prevents congestion that can occur if all routing devices update their neighbors simultaneously.
To configure the update time interval, include the update-interval statement:
seconds can be a value from 10 through 60.
You can set a route timeout interval. If a route is not refreshed after being installed in the routing table by the specified time interval, the route is marked as invalid and is removed from the routing table after the hold-down period expires.
To configure the route timeout for RIP, include the route-timeout statement:
seconds can be a value from 30 through 360. The default value is 180 seconds.
RIP routes expire when either a route timeout limit is met or a route metric reaches infinity, and the route is no longer valid. However, the expired route is retained in the routing table for a specified period so that neighbors can be notified that the route has been dropped. This time period is set by configuring the hold-down timer. Upon expiration of the hold-down timer, the route is removed from the routing table.
To configure the hold-down timer for RIP, include the holddown statement:
seconds can be a value from 10 through 180. The default value is 120 seconds.
In Junos OS Release 11.1 and later, a retransmission timer is available for RIP demand circuits.
Generally, we recommend against changing the RIP timers, unless the effects of a change are well understood. The route timeout should be at least three times the update interval. Normally, the default values are best left in effect for standard operations.