The answer is a mismatched OSPF hello interval between the two routers. When a router is stuck in the INIT state, it has received a Hello packet from its neighbor, but the neighbor has not yet seen its own Router ID in the returning Hello—meaning the two-way communication required to advance past INIT has failed. A hello interval mismatch causes each router to send Hellos at different rates, so one router may miss a Hello before the Dead interval expires, preventing the neighbor from ever seeing its Router ID in the received Hello. On the ENCOR 350-401 exam, this scenario tests your understanding of OSPF neighbor state progression and the critical role of timer consistency; a common trap is to blame subnet mismatches or authentication, but those typically cause a different state (like DOWN or EXSTART). Remember the memory tip: INIT means “I heard you, but you haven’t heard me yet”—if timers don’t match, that two-way handshake never completes.
CCNP OSPF Practice Question
This 350-401 practice question tests your understanding of ospf. The scenario asks you to isolate a root cause — eliminate options that address a different problem before choosing. After answering, compare your reasoning against the explanation and wrong-answer breakdown below. Once you have made your selection, read the full explanation to reinforce the concept and understand why each distractor is designed to mislead on exam day.
A network engineer is troubleshooting an OSPF adjacency issue between two routers connected via a serial link. The adjacency is stuck in the INIT state. The engineer has verified that the IP addresses are in the same subnet and that the link is up. What is the most likely cause?
Clue words in this question
Noticing these words before you look at the options changes how you read each choice.
Clue: "most likely"
Why it matters: Probability qualifier — the question wants the most probable cause or outcome, not a guaranteed one. Eliminate low-probability options.
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
The OSPF hello interval is mismatched between the two routers.
The INIT state in OSPF indicates that a router has received a Hello packet from its neighbor but the neighbor has not yet seen its own Router ID in the received Hello. A mismatched Hello interval causes the routers to send Hellos at different rates, so one router may not receive a Hello within the expected Dead interval, preventing the neighbor from seeing its Router ID in the received Hello and thus stalling the adjacency in INIT.
Key principle: Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
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 router IDs are the same.
Why it's wrong here
Incorrect because duplicate router IDs would cause the adjacency to fail at a later state, not INIT.
✓
The OSPF hello interval is mismatched between the two routers.
Why this is correct
Correct because if the hello intervals are different, the routers will not agree on the hello timer, causing the adjacency to remain in INIT.
Clue confirmation
The clue word "most likely" in the question point toward this answer.
Related concept
Read the scenario before looking for a memorised answer.
✗
The OSPF process ID is different.
Why it's wrong here
Incorrect because OSPF process ID is locally significant and does not affect adjacency formation.
✗
The OSPF network type is point-to-point on one router and point-to-multipoint on the other.
Why it's wrong here
Incorrect because network type mismatch typically causes issues in the 2WAY state, not INIT.
Common exam traps
Common exam trap: answer the scenario, not the keyword
Cisco often tests the distinction between INIT and other OSPF states, and the trap here is that candidates confuse a network type mismatch (which causes EXSTART issues) with a Hello interval mismatch (which causes INIT), or incorrectly assume that the OSPF process ID must match.
Detailed technical explanation
How to think about this question
OSPF uses Hello and Dead intervals that must match for adjacency to form; the Dead interval defaults to 4 times the Hello interval. On serial links, the network type often defaults to point-to-point (no DR/BDR), but if the Hello intervals differ, the router with the shorter Hello interval will not see its Router ID in the neighbor's Hello within the Dead interval, keeping the state in INIT. Real-world misconfigurations often occur when one side is set to a non-default Hello interval (e.g., for faster convergence) without updating the neighbor.
KKey Concepts to Remember
Read the scenario before looking for a memorised answer.
Find the constraint that changes the correct option.
Eliminate answers that are true in general but not in this case.
TExam Day Tips
→Watch for words such as best, first, most likely and least administrative effort.
→Review why wrong options are wrong, not only why the correct option is correct.
Key takeaway
Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Real-world example
How this comes up in practice
A network engineer at a university connects two campus buildings via a fibre link. Both routers run OSPF, but no adjacency forms — even though both routers can ping each other. The engineer finds one router is in area 0 and the other in area 1. OSPF adjacency requires matching area numbers, hello/dead timers, and network type. IP reachability alone is not enough.
What to study next
Got this wrong? Here's your next step.
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
OSPF — This question tests OSPF — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: The OSPF hello interval is mismatched between the two routers. — The INIT state in OSPF indicates that a router has received a Hello packet from its neighbor but the neighbor has not yet seen its own Router ID in the received Hello. A mismatched Hello interval causes the routers to send Hellos at different rates, so one router may not receive a Hello within the expected Dead interval, preventing the neighbor from seeing its Router ID in the received Hello and thus stalling the adjacency in INIT.
What should I do if I get this 350-401 question wrong?
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
Are there clue words in this question I should notice?
Yes — watch for: "most likely". Probability qualifier — the question wants the most probable cause or outcome, not a guaranteed one. Eliminate low-probability options.
What is the key concept behind this question?
Read the scenario before looking for a memorised answer.
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Question Discussion
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