An OSPF neighbor entry is a router-maintained record for a discovered OSPF router. It records the neighbor’s router ID, state, dead time, address, and interface, helping verify whether routers recognize one another. section 18.3.1
An entry progresses as routers exchange hello messages:
- Down means no hello has been received on the interface. section 18.3.1
- Init means a hello arrived, but it did not include the local router ID. section 18.3.1
- 2-Way means both routers see and acknowledge each other; some neighbors remain there, while others progress toward adjacency. section 18.3.1
Checking the neighbor table
Run show ip ospf neighbor. For example, R2 can display R1 as 172.16.1.1 in INIT/DROTHER on GigabitEthernet0/0, while R1 can display R2 as 172.16.1.2 in 2WAY/DROTHER.
