RIP Timers

RIP uses four different kinds of timers to regulate its performance:

Route update timer   Sets the interval (typically 30 seconds) between periodic routing updates
in which the router sends a complete copy of its routing table out to all neighbors.

Route invalid timer   Determines the length of time that must elapse (180 seconds) before a
router determines that a route has become invalid. It will come to this conclusion if it hasn’t
heard any updates about a particular route for that period. When that happens, the router will
send out updates to all its neighbors letting them know that the route is invalid.

Holddown timer   This sets the amount of time during which routing information is sup-
pressed. Routes will enter into the holddown state when an update packet is received that indi-
cated the route is unreachable. This continues either until an update packet is received with a
better metric or until the holddown timer expires. The default is 180 seconds.

Route flush timer   Sets the time between a route becoming invalid and its removal from the
routing table (240 seconds). Before it’s removed from the table, the router notifies its neigh-
bors of that route’s impending demise. The value of the route invalid timer must be less than
that of the route flush timer. This gives the router enough time to tell its neighbors about the
invalid route before the local routing table is updated.

ref.: Cisco Certified Network Associate Study Guide