OSPF Neighbor Adjacency Failures

OSPF Neighbor States

• Down: No Hello packets received.
• Attempt (Only in NBMA networks): waiting for Hello reply after actively sending.
• Init: Hello received, but own Router ID not seen by neighbor yet.
• 2-Way: Hello exchanged, bidirectional communication confirmed.
• ExStart/Exchange: Master/slave negotiation, start of database exchange.
• Loading/Full: LSAs exchanged; Full means neighbor is fully established.

The Down state means no Hello packets are received. This state does not appear in show ip ospf neighbor output.