OSPF Fast Hellos Lab

OSPF Fast Hellos Lab
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.
OSPF fast hellos allow you to configure sub-second convergence. The RouterDeadInterval is fixed at 1 second while hello messages are sent in fractions of a second. While all OSPF neighbors must agree to user fast hellos, the HelloInterval does not have to match (technically is will match as it will be set to 0). OSPF fast hellos are great for LAN segments that require fast convergence (MANs and Data Centers).

[@csmakio]

Thanks for the great videos by the way

[@csmakio]

What simulation software are you running for your networks? GNS3?