OSPF Hello packets discover and maintain relationships with neighbouring OSPF routers.
Hello packets in most default configurations send to the multicast address 126.96.36.199
|Router ID||A unique 32-bit ID within the OSPF domain|
|Authentication Options||Allows secured communications between OSPF routers. Can be set to: none, clear text or MD5 authentication|
|Area ID||The OSPF area that the OSPF interface is associated to. It can be in dotted decimal format or as a decimal.|
|Interface Address Mask||The network mask for the primary IP address associated with the interface that the Hello packet is sourced from|
|Interface Priority||The interface priority for OSPF DR elections|
|Hello Interval||The interval in seconds that the source router will send out hello packets|
|Dead Interval||The interval in seconds that the source router will wait until it declares the neighbour router as down|
|Designated router and designed backup router||The IP addresses of the DR and BDR routers in the network link|
|Active Neighbour||A list of OSPF neighbours that have been seen on the network segment|
The default Hello timer is based on the OSPF network type. The Hello timer can be modified in the interface configuration mode with the command
ip ospf hello-interval with a value between 1 and 65535
The dead timer will be modified too as a result of the Hello timer change, but it too can be changed with the command
ip ospf dead-interval with a value between 1 and 65535
Make sure that the OSPF dead timer is greater than the hello timer.
Hello and Dead timers can be verified with the command
show ip ospf interface
Neighbours timers must match in order for them to become adjacent.