OSPF Neighbor States

OSPF routers go through several states to establish full adjacency with their neighbors. Understanding these states is crucial for troubleshooting OSPF.

Neighbor States:

  1. Down: No Hellos received from neighbor.
  2. Attempt: (NBMA networks) Neighbor is manually configured, but no Hellos received.
  3. Init: Hellos received, but router's own Router ID not in Hello.
  4. 2-Way: Hellos received, and router's own Router ID is in Hello. DR/BDR election occurs here.
  5. ExStart: Master/Slave negotiation and initial DBD sequence number exchange.
  6. Exchange: DBDs (Database Description packets) exchanged.
  7. Loading: LSA requests and updates exchanged.
  8. Full: Routers have synchronized their LSDBs and are fully adjacent.