Which OSPF neighbor state indicates a fully formed adjacency?

• A. Down
• B. Init
• C. ExStart
• D. Full

Answer: (D)

In OSPF, neighbors progress through states as they establish a relationship and synchronize their routing databases. The state that means the adjacency is fully formed is the moment when both routers have completed exchanging their database information and their Link-State Databases are identical, so they can reliably share routing data.

This final state occurs after the series of steps where the routers exchange database descriptions, requests, and acknowledgments, completing the synchronization. When both sides have a complete and matching view of the network’s LSAs, the adjacency is considered fully formed, and normal routing operations can proceed.

Earlier states represent partial progress: Down means no neighbor is detected; Init means a hello was received from the neighbor but you haven’t seen your own router ID in its hello yet; ExStart is the negotiation phase that sets up how the exchange will happen. Those precede the final, fully synchronized state.