OSPF Neighbours/Adjacencies

Routers running OSPF need to be directly connected in order to form adjacencies, routers exchange hello messages and update their respective neighbour tables.

Hello messages are sent to multicast address: 224.0.0.5

*Mar 1 00:17:10.235: OSPF: Send hello to 224.0.0.5 area 51 on FastEthernet0/0 from 192.168.0.2
*Mar 1 00:17:11.503: OSPF: Rcv hello from 192.168.0.1 area 51 from FastEthernet0/0 192.168.0.1
*Mar 1 00:17:11.503: OSPF: End of hello processing

Router1#sh ip ospf neighbor
Neighbor ID Pri State Dead Time Address Interface
192.168.0.1 1 FULL/BDR 00:00:28 192.168.0.1 FastEthernet0/0

Router2#sh ip ospf neighbor
Neighbor ID Pri State Dead Time Address Interface
192.168.0.2 1 FULL/DR 00:00:39 192.168.0.2 FastEthernet0/0

Hello messages are sent every 10 seconds on a broadcast link, or every 30 seconds on a non-broadcast link.