OSPF Fast Hello

Normal OSPF timers could be configured defining the hello-interval and dead-interval, as hello interval is 1 sec, detect a dead neighbor within 1 second means at first loss of a hello.

ip ospf hello-interval 1-65535s
ip ospf dead-interval 1-65535s


Fast hello permit a hello-interval below 1sec. The following command means hello of 333ms and a dead-interval of 1sec :

ip ospf dead-interval minimal hello-multiplier 3