- A
The neighbor is configured as an EIGRP stub router.
Correct because a stub router only advertises connected and summary routes by default, so if the neighbor has other routes, they will not be advertised.
- B
The local router has a distribute-list out applied to the neighbor.
Why wrong: Incorrect because a distribute-list out would filter routes going out to the neighbor, not incoming routes.
- C
The EIGRP metric weights are different on the two routers.
Why wrong: Incorrect because mismatched metric weights prevent adjacency formation, not route advertisement after adjacency is up.
- D
The local router has a route-map applied to the EIGRP process that is filtering all routes.
Why wrong: Incorrect because a route-map applied to the EIGRP process would affect redistribution, not the reception of routes from a neighbor.
Quick Answer
The answer is that the neighbor is configured as an EIGRP stub router. When a router is configured as an EIGRP stub, it restricts the types of routes it advertises to its neighbors, typically sending only connected and summary routes while withholding all other learned routes. This explains why the adjacency is up—the neighbor relationship forms normally—but no routes appear in the topology table, even though the neighbor has routes to advertise. On the Cisco CCNP ENARSI 300-410 exam, this scenario tests your understanding of EIGRP stub behavior and its impact on route propagation, often appearing as a troubleshooting trap where candidates mistakenly blame distribute-lists or authentication issues. A common memory tip is to remember that a stub router is a "quiet neighbor"—it listens but only speaks a few specific route types, so if you see an up adjacency with zero received routes, think "stub first."
300-410 EIGRP Troubleshooting Practice Question
This 300-410 practice question tests your understanding of eigrp troubleshooting. 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.
An engineer is troubleshooting an EIGRP issue where a router is not learning any routes from a neighbor, but the neighbor adjacency is up. The engineer checks the EIGRP topology table on the local router and sees that the neighbor is listed, but no routes from that neighbor are present. The engineer also verifies that the neighbor has routes to advertise. 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 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 neighbor is configured as an EIGRP stub router.
If the adjacency is up but no routes are received, the issue is likely that a distribute-list is filtering incoming routes, or the neighbor is configured as a stub router. In this case, the most common cause is that the neighbor is configured as a stub router, which restricts the routes it advertises.
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.
- ✓
The neighbor is configured as an EIGRP stub router.
Why this is correct
Correct because a stub router only advertises connected and summary routes by default, so if the neighbor has other routes, they will not be advertised.
Clue confirmation
The clue word "most likely" in the question point toward this answer.
Related concept
OSPF neighbours must agree on key parameters.
- ✗
The local router has a distribute-list out applied to the neighbor.
Why it's wrong here
Incorrect because a distribute-list out would filter routes going out to the neighbor, not incoming routes.
- ✗
The EIGRP metric weights are different on the two routers.
Why it's wrong here
Incorrect because mismatched metric weights prevent adjacency formation, not route advertisement after adjacency is up.
- ✗
The local router has a route-map applied to the EIGRP process that is filtering all routes.
Why it's wrong here
Incorrect because a route-map applied to the EIGRP process would affect redistribution, not the reception of routes from a neighbor.
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.
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?
EIGRP Troubleshooting — This question tests EIGRP Troubleshooting — OSPF neighbours must agree on key parameters..
What is the correct answer to this question?
The correct answer is: The neighbor is configured as an EIGRP stub router. — If the adjacency is up but no routes are received, the issue is likely that a distribute-list is filtering incoming routes, or the neighbor is configured as a stub router. In this case, the most common cause is that the neighbor is configured as a stub router, which restricts the routes it advertises.
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.
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?
OSPF neighbours must agree on key parameters.
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Last reviewed: Jun 18, 2026
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