The answer is that the OSPF adjacency with 10.0.0.2 is forming successfully and will reach the FULL state. This is correct because the debug output shows the complete sequence of OSPF adjacency formation over a DMVPN tunnel: the router first establishes two-way communication (2WAY state), then proceeds to exchange Database Description (DBD) packets with the appropriate flags, and finally completes the Exchange state, which is the final prerequisite before the adjacency transitions to FULL. On the Cisco CCNP ENARSI 300-410 exam, this scenario tests your ability to interpret OSPF neighbor states specifically in a DMVPN hub-and-spoke environment, where the NBMA or point-to-multipoint network type can cause adjacencies to stall at 2WAY or EXSTART if misconfigured. A common trap is confusing the 2WAY state with a problem, but here it is a normal step, and the subsequent DBD exchange confirms the adjacency is progressing. Memory tip: remember the OSPF adjacency states as "Down, Attempt, Init, 2WAY, ExStart, Exchange, Loading, Full" — and note that "2WAY" is actually a healthy state for broadcast networks, not a failure.
300-410 DMVPN Practice Question
This 300-410 practice question tests your understanding of dmvpn. 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 runs the following command to troubleshoot OSPF over DMVPN:
R1# debug ip ospf adj
OSPF: 2 Way Communication to 10.0.0.2 on Tunnel0, state 2WAY
OSPF: Send DBD to 10.0.0.2 on Tunnel0 seq 0x1234 opt 0x52 flag 0x7
OSPF: Rcv DBD from 10.0.0.2 on Tunnel0 seq 0x1235 opt 0x52 flag 0x2
OSPF: Exchange Done with 10.0.0.2 on Tunnel0
OSPF: Build router LSA for area 0, router ID 1.1.1.1
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
OSPF adjacency with 10.0.0.2 is forming successfully and will reach FULL state.
The debug shows OSPF adjacency formation: 2-way state, database description exchange, and exchange done, indicating a full adjacency is being established.
Key principle: OSPF neighbour adjacency depends on matching area, hello/dead timers, network type, and authentication — IP reachability alone is not enough.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
✗
OSPF adjacency with 10.0.0.2 is stuck in 2WAY state and not progressing.
Why it's wrong here
Incorrect because the output shows DBD exchange and exchange done.
✓
OSPF adjacency with 10.0.0.2 is forming successfully and will reach FULL state.
Why this is correct
Correct: The sequence shows normal adjacency formation steps.
Incorrect because OSPF packets are being sent and received.
✗
There is an OSPF MTU mismatch causing the adjacency to fail.
Why it's wrong here
Incorrect because there is no indication of MTU issues.
Common exam traps
Common exam trap: OSPF can fail even when IP connectivity looks correct
OSPF neighbour formation depends on matching areas, timers, network type, authentication and passive-interface behaviour. Do not choose an answer only because the devices can ping.
Trap categories for this question
Command / output trap
Incorrect because the output shows DBD exchange and exchange done.
Detailed technical explanation
How to think about this question
OSPF questions usually test the details that control adjacency and route selection. Read the neighbour state, area, router ID and interface configuration before deciding what is wrong.
KKey Concepts to Remember
OSPF neighbours must agree on key parameters.
Router ID selection can affect neighbour relationships and LSDB output.
OSPF cost influences the preferred path.
A route can appear in OSPF information but not become the installed route.
TExam Day Tips
→Check area mismatch first when OSPF adjacency fails.
→Review passive interfaces when a network is advertised but no neighbour forms.
→Use show ip ospf neighbor and show ip route clues carefully.
Key takeaway
OSPF neighbour adjacency depends on matching area, hello/dead timers, network type, and authentication — IP reachability alone is not enough.
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.
Related glossary terms
Concepts from this question explained
These glossary pages explain the core terms tested in this 300-410 question in full detail.
Review OSPF neighbour requirements — matching area type, hello and dead timers, network type, stub flags, and authentication. Study show ip ospf neighbor states (INIT, 2-WAY, FULL). Then practise related 300-410 OSPF questions on adjacency and route selection.
DMVPN — This question tests DMVPN — OSPF neighbours must agree on key parameters..
What is the correct answer to this question?
The correct answer is: OSPF adjacency with 10.0.0.2 is forming successfully and will reach FULL state. — The debug shows OSPF adjacency formation: 2-way state, database description exchange, and exchange done, indicating a full adjacency is being established.
What should I do if I get this 300-410 question wrong?
Review OSPF neighbour requirements — matching area type, hello and dead timers, network type, stub flags, and authentication. Study show ip ospf neighbor states (INIT, 2-WAY, FULL). Then practise related 300-410 OSPF questions on adjacency and route selection.
What is the key concept behind this question?
OSPF neighbours must agree on key parameters.
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