- A
One router has 'ip ospf network point-to-point' configured, while the other uses the default broadcast, causing a mismatch in the network type.
A network type mismatch prevents proper OSPF operation; broadcast expects DR/BDR election, while point-to-point does not, leading to inconsistent neighbor states and potential forwarding issues.
- B
The FastEthernet interface is operating at half-duplex, causing packet loss.
Why wrong: Duplex mismatch could cause issues, but the OSPF neighbor state would not show FULL/DR if that were the case.
- C
OSPF hello and dead timers are mismatched, preventing adjacency formation.
Why wrong: The neighbor state is FULL, so timers are consistent.
- D
The MTU on the link is mismatched, causing OSPF packets to be dropped.
Why wrong: MTU mismatch typically prevents adjacency from forming, but here it is FULL.
Quick Answer
The answer is an OSPF network type mismatch, where one router has the interface manually configured as point-to-point while the other retains the default broadcast setting. This is correct because the `show ip ospf interface` output on R1 indicating point-to-point directly contradicts the DR/BDR election states seen in the neighbor table—broadcast requires a DR/BDR, but point-to-point does not. Although the adjacency reaches FULL, the mismatch corrupts the forwarding database, causing intermittent ping failures despite routes appearing in the table. On the Cisco CCNP ENARSI 300-410 exam, this scenario tests your ability to correlate `show ip ospf interface` and `show ip ospf neighbor` outputs to spot configuration inconsistencies, a common trap where candidates assume FULL adjacency guarantees correct traffic flow. Remember the memory tip: “If the interface type says point-to-point but the neighbor table shows a DR, you’ve got a mismatch that will break your flow.”
300-410 Device Management Practice Question
This 300-410 practice question tests your understanding of device management. Examine the command output carefully: the correct answer depends on what the output actually shows, not on general recall alone. 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.
Two routers R1 and R2 are connected via a FastEthernet link. OSPF is configured on both with network type broadcast. R1 shows: 'show ip ospf neighbor' lists R2 as FULL/DR. R2 shows: 'show ip ospf neighbor' lists R1 as FULL/BDR. However, pings between loopback interfaces on R1 and R2 fail intermittently. 'show ip route' on R1 shows the loopback of R2 as reachable via OSPF, but 'show ip ospf interface' on R1 shows the link as point-to-point. What is the root 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
One router has 'ip ospf network point-to-point' configured, while the other uses the default broadcast, causing a mismatch in the network type.
The 'show ip ospf interface' output indicating point-to-point suggests that the interface has been manually configured as OSPF network type point-to-point, but the neighbor state shows DR/BDR election, which is inconsistent. This mismatch causes OSPF to form adjacency but with incorrect forwarding behavior. The actual configuration likely has 'ip ospf network point-to-point' on one router but not the other, leading to a mismatch. The fix is to ensure consistent network type.
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.
- ✓
One router has 'ip ospf network point-to-point' configured, while the other uses the default broadcast, causing a mismatch in the network type.
- ✗
The FastEthernet interface is operating at half-duplex, causing packet loss.
Why it's wrong here
Duplex mismatch could cause issues, but the OSPF neighbor state would not show FULL/DR if that were the case.
- ✗
OSPF hello and dead timers are mismatched, preventing adjacency formation.
Why it's wrong here
The neighbor state is FULL, so timers are consistent.
- ✗
The MTU on the link is mismatched, causing OSPF packets to be dropped.
Why it's wrong here
MTU mismatch typically prevents adjacency from forming, but here it is FULL.
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
Duplex mismatch could cause issues, but the OSPF neighbor state would not show FULL/DR if that were the case.
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.
What to study next
Got this wrong? Here's your next step.
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.
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FAQ
Questions learners often ask
What does this 300-410 question test?
Device Management — This question tests Device Management — OSPF neighbours must agree on key parameters..
What is the correct answer to this question?
The correct answer is: One router has 'ip ospf network point-to-point' configured, while the other uses the default broadcast, causing a mismatch in the network type. — The 'show ip ospf interface' output indicating point-to-point suggests that the interface has been manually configured as OSPF network type point-to-point, but the neighbor state shows DR/BDR election, which is inconsistent. This mismatch causes OSPF to form adjacency but with incorrect forwarding behavior. The actual configuration likely has 'ip ospf network point-to-point' on one router but not the other, leading to a mismatch. The fix is to ensure consistent network type.
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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Last reviewed: Jun 18, 2026
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.
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