OSPF - Neighbor states

When deploying an OSPF topology, you can observe the status of the OSPF neighbors by issuing the show ip ospf neighbors command like so:

R2#show ip ospf neighbor 

Neighbor ID   Pri   State     Dead Time   Address       Interface
192.168.13.1    1   FULL/BDR  00:00:31    192.168.12.1  Ethernet0/0
3.3.3.3         1   FULL/DR   00:00:38    192.168.23.3  FastEthernet1/0

Under the State column, the following is shown:

STATE/ROLE

The STATE indicates the current state of the OSPF adjacency, and can be any of the following:

• Down: The initial state where no OSPF information has been received from a neighbor, but hello packets can still be sent.
• Attempt: In NBMA environments, the router sends unicast hello packets to a manually configured neighbor from which no hellos have been received.
• Init: A state where a router has received a hello packet from a neighbor, but its own ID is not listed in the hello packet.
• 2-Way: Indicates bi-directional communication has been established, where each router sees its own ID in the neighbor's hello packet; used to determine adjacency formation.
• Exstart: The routers and DR/BDR establish a primary-secondary relationship and choose an initial sequence number for database synchronization.
• Exchange: Routers exchange database descriptor packets to describe the contents of their link-state databases and begin synchronizing link-state information.
• Loading: Routers exchange full link-state information based on requests generated from received DBD packets.
• Full: Routers are fully adjacent, with all link-state information exchanged and databases fully synchronized, indicating normal OSPF operation.

The ROLE desribes the role that the indicated neighbor has with regard to the DR and the BDR It can be any of the following:

• DR - This indicates that the neighbor is a Designated Router on this network segment.
• BDR - This indicates that the negibor is the Backup Designated Router on this network segment
• DROTHER - This indicates that the neighbor is neither the DR nor the BDR on the network segment
• -- - This indicates that the configured OSPF network type is one where a DR/BDR election does not take place.

Links:

https://networklessons.com/ospf/basic-ospf-configuration

https://www.cisco.com/c/en/us/support/docs/ip/open-shortest-path-first-ospf/13688-16.html

https://www.cisco.com/c/en/us/support/docs/ip/open-shortest-path-first-ospf/13685-13.html