OSPF Neighbor Relationship Established State
Short answer
D The 2-way state indicates that the OSPF neighbor relationship has been established, confirming bidirectional communication between routers.
Question
Key Takeaways
The main trap is confusing 'neighbor relationship' (2-way) with 'adjacency' (Full). Neighbors become adjacencies only after DBD/LSR/LSU exchanges complete.
Identify the OSPF state that signifies an established neighbor relationship. The correct answer is the 2-way state, which confirms bidirectional Hello exchange, distinct from the Full adjacency state.
Common mistake: Choosing Full (B) because it represents the final stable state. However, Full denotes LSDB synchronization (adjacency), whereas 2-way is the specific threshold for establishing the neighbor relationship itself.
Expert Analysis
The question asks for the state indicating that an OSPF neighbor relationship has been established. In OSPF terminology, there is a critical distinction between a 'neighbor' and an 'adjacency'.
Neighbor Relationship (2-Way State) The OSPF neighbor relationship is considered 'established' when bidirectional communication is confirmed. This occurs in the 2-way state. At this point, each router has seen its own Router ID in the neighbor's Hello packet. For non-DR/BDR routers on multi-access networks, the process stops here; they remain neighbors but do not form adjacencies. Therefore, '2-way' is the definitive state where the neighbor relationship is established.
Adjacency (Full State) The Full state indicates that an adjacency has been formed and the Link State Databases (LSDBs) are fully synchronized. While all Full states imply a neighbor relationship exists, not all neighbor relationships reach the Full state. The question specifically uses the term 'neighbor relationship', which maps technically to the 2-way state.
Other States
- Down: No Hello packets have been received.
- Attempt: Used only on NBMA networks with manual neighbor configuration, indicating periodic Hellos are being sent but no response received.
The comment arguing for 'Full' confuses adjacency with neighbor relationship. The comment supporting '2-way' correctly identifies that 2-way confirms the neighbor relationship via bidirectional Hello exchange.
Exam Strategy
When answering OSPF state questions, carefully distinguish between 'neighbor' and 'adjacency'. If the question asks about the neighbor relationship or Hello exchange confirmation, think '2-way'. If it asks about database synchronization or full connectivity, think 'Full'. Memorize the progression: Init -> 2-Way -> ExStart -> Exchange -> Loading -> Full.
Frequently Asked Questions
What is the difference between OSPF neighbor and adjacency?
Why is the Attempt state used in OSPF?
Community Votes
50% of anonymous learners picked answer B. Votes are pick records left by other test-takers — they are not the verified answer.
Discussion 2 contributions
Compiled from public community threads and reader submissions, lightly edited for clarity. Handles and vote tallies are shown as recorded, and comments reflect the views of individual contributors.
From public community threads 2
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e9b92a4 👍 1 Answered DD. 2-way Explanation: 2‑way means each router has seen its own Router ID in the neighbor’s Hello—bidirectional communication is confirmed and the OSPF neighbor relationship is established. Full means an adjacency is established and LSDBs are fully synchronized (this happens with DR/BDR on multi‑access networks or on point‑to‑point links). Down means no Hellos have been received. Attempt is used on NBMA networks when trying to contact a neighbor that hasn’t been heard from yet.
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Fmoura17 👍 1 Answered BB. Full ✅ The Full state indicates that the OSPF neighbor relationship has been completely and successfully established. Both routers have synchronized their Link State Databases (LSDBs) and are fully adjacent. This is the final and desired state for OSPF neighbors.
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