OSPF Timers - Hello and Dead Intervals - Part 2

The HelloInterval and RouterDeadInterval are the two timers that you can adjust to speed up network convergence in an OSPF network. The HelloInterval determines the interval between sending OSPF Hello messages on an interface, while the RouterDeadInterval is the interval in which a router must receive an OSPF Hello message from a neighbor before it considers that neighbor to be down.

Cisco IOS assigns a default HelloInterval and RouterDeadInterval to OSPF enabled interfaces. Depending on the interface type, the HelloInterval will be either 10 seconds or 30 seconds. The RouterDeadInterval will be four times the HelloInterval (40 or 120 seconds). A Cisco OSPF-enabled device will maintain a count down timer for each neighbor based on the RouterDeadInterval. Each time receives a Hello message from a neighbor, it will reset this timer to the RouterDeadInterval. If it does not receive a Hello message before this timer expires, then the neighbor will be set to the OSPF DOWN state.

You can adjust the HelloInterval and RouterDeadInterval with the ip ospf hello-interval and ip ospf dead-interval interface configuration commands. Doing so can reduce OSPF convergence, but you should be careful to take into consideration the quality (and possibly speed) of your links before doing so.