OSPF Timers Open Shortest Path First

OSPF forms new neighbour relationships, and detects current neighbours who have gone down through the use of hello and dead timers. These timers have a default value depending on the type of interface over which hellos are sent and received, and can be manipulated by us to improve convergence time and neighbour stability.

Hello timer

The hello timer defines the interval between the sending of hellos onto a link. The default rate at which it sends hellos varies based on the type of interface: 10 seconds for broadcast and point to point links, and 30 seconds for all other types.

Router(config-if)#ip ospf hello-interval <value>

As you can see, we can manipulate the hello timer value from interface configuration mode with the command above, where value is any integer in the range 1-65535 seconds.

Dead timer

The dead timer defines how long I should wait after receiving the last hello before I consider that neighbour dead. The rule of thumb is that this value will be 4 times larger than the hello timer, which makes the default dead timer on broadcast and point to point networks 40 seconds, and 120 seconds on all others. As you can see, this is a significant waiting time, and you may wish to reduce this value to speed convergence.

Router(config-if)#ip ospf dead-interval <value>

As with the hello timer, the dead timer is configured from interface configuration mode and is assigned a value in the range of 1-65535 seconds.

A few points

There are a few things to bare in mind with these timers.

Further reading