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300-410 Practice Question: Is troubleshooting an OSPF adjacency that is not…
A network engineer is troubleshooting an OSPF adjacency that is not forming. Both routers are running OSPF with BFD enabled. The engineer checks the BFD session and sees it is 'Up'. However, the OSPF neighbor state is stuck in 'INIT'. What is the most likely cause?
Answer choices
Why each option matters
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
The OSPF area ID is mismatched between the two routers.
OSPF stuck in INIT usually indicates that the router is not receiving OSPF hello packets from the neighbor. BFD being up suggests Layer 2 connectivity is fine, so the issue is likely OSPF configuration, such as a mismatch in area ID or authentication.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
The OSPF hello interval is mismatched between the two routers.
Why it's wrong here
A hello interval mismatch would cause the neighbor to go to DOWN or EXSTART, not INIT.
- ✗
The OSPF network type is mismatched (e.g., broadcast vs point-to-point).
Why it's wrong here
Network type mismatch can cause issues, but it typically results in the neighbor being stuck in EXSTART or 2WAY, not INIT.
- ✓
The OSPF area ID is mismatched between the two routers.
Why this is correct
If the area ID does not match, the router will ignore the hello packets, causing the neighbor to remain in INIT state.
- ✗
The interface is configured with 'ip ospf bfd' but the OSPF process is not configured with 'bfd all-interfaces'.
Why it's wrong here
This would prevent BFD from working, but the BFD session is up, so this is not the issue.
Visual reference
Quick reference
Routing Protocol Comparison
| Protocol | Metric | Max Hops | Algorithm | Type |
|---|---|---|---|---|
| RIP v2 | Hop count | 15 | Bellman-Ford | Distance vector |
| OSPF | Cost (bandwidth) | Unlimited | Dijkstra (SPF) | Link state |
| EIGRP | Composite metric | Unlimited | DUAL | Hybrid |
| IS-IS | Cost | Unlimited | Dijkstra | Link state |
| BGP | Policy / attributes | Unlimited | Path vector | Path vector |
RIP's 15-hop limit makes it unsuitable for large networks. OSPF and EIGRP dominate modern enterprise deployments.
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Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
This 300-410 practice question is part of Courseiva's free Cisco certification practice question bank. Courseiva provides original exam-style practice questions with explanations, topic-based practice, mock exams, readiness tracking, and study analytics to help learners prepare for the 300-410 exam.