Question 1,303 of 2,152

EIGRP Troubleshooting →easyMultiple ChoiceObjective-mapped

EIGRP No Routes Received Despite Adjacency: Distribute-List

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.

A network 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 and sees that the neighbor is listed, but no routes are present. The engineer also checks the interface configuration and sees that the interface is configured as a passive interface under the EIGRP process. What is the most likely cause of the issue?

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.

A
The passive-interface command is preventing the router from sending updates, but not receiving them.
Why wrong: Incorrect because passive-interface prevents both sending and receiving hellos, so adjacency would not form.
B
The neighbor is configured with a distribute-list that filters all routes.
Correct because if the adjacency is up but no routes are received, the neighbor is likely filtering the routes it sends.
C
The EIGRP process is configured with the 'no auto-summary' command.
Why wrong: Incorrect because auto-summary affects route summarization at classful boundaries, not the reception of routes.
D
The router ID is not configured, so EIGRP is using the highest loopback IP.
Why wrong: Incorrect because the router ID does not affect the ability to receive routes.

Full breakdown with real-world context →

Quick Answer

The answer is a distribute-list configured on the neighbor that filters all outbound routes. When an EIGRP adjacency is up but no routes are received, the issue lies in route filtering, not in neighbor formation. A passive-interface command would prevent the adjacency from forming entirely, since it stops hello packets; because the adjacency is up, passive-interface is ruled out. This scenario tests your ability to distinguish between layer 3 reachability issues and route advertisement controls on the Cisco CCNP ENARSI 300-410 exam, where a common trap is to blame passive-interface when the adjacency is already established. The distribute-list applied outbound on the neighbor silently drops all routes from being sent, leaving the topology table empty despite a full neighbor relationship. Memory tip: if the neighbor is up but the table is bare, check the filter—passive kills the handshake, distribute-list kills the payload.

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 with a distribute-list that filters all routes.

The scenario as described is internally inconsistent: if the interface facing the neighbor is configured as passive under the EIGRP process, the router stops sending hellos on that interface. Without receiving hellos from the local router, the neighbor adjacency would eventually fail. Since the adjacency is reported as up, the passive-interface configuration cannot be affecting this interface (or the adjacency would not be stable). Therefore, the passive-interface is not the issue. The most likely cause is that the neighbor has a distribute-list applied that filters all routes, preventing any routes from being advertised to the local router, even though the adjacency is established.

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 passive-interface command is preventing the router from sending updates, but not receiving them.
Why it's wrong here
Incorrect because passive-interface prevents both sending and receiving hellos, so adjacency would not form.
✓
The neighbor is configured with a distribute-list that filters all routes.
Why this is correct
Correct because if the adjacency is up but no routes are received, the neighbor is likely filtering the routes it sends.
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 EIGRP process is configured with the 'no auto-summary' command.
Why it's wrong here
Incorrect because auto-summary affects route summarization at classful boundaries, not the reception of routes.
✗
The router ID is not configured, so EIGRP is using the highest loopback IP.
Why it's wrong here
Incorrect because the router ID does not affect the ability to receive routes.

Common exam traps

Common exam trap: answer the scenario, not the keyword

This question presents a contradictory scenario: a passive interface under EIGRP prevents the router from sending or receiving hello packets, so no neighbor adjacency can form. Yet the adjacency is stated as up. The trap is that candidates may focus on the passive-interface as the cause, but since adjacency exists, it cannot be the issue. The only logical explanation is an inbound filter (distribute-list) on the neighbor side that drops all routes while allowing hello packets to maintain adjacency.

Detailed technical explanation

How to think about this question

EIGRP distribute-lists use access-lists or prefix-lists to filter routes in the inbound or outbound direction. When applied inbound on a neighbor, the local router will still form the adjacency (since hello packets are not filtered), but the filtered routes are never installed in the topology table. This is a common troubleshooting scenario where an engineer sees an established neighbor but an empty topology table, pointing to a filter or a mismatch in the EIGRP K-values or autonomous system number.

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.

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.

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.

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FAQ

Questions learners often ask

What does this 300-410 question test?

EIGRP Troubleshooting — This question tests EIGRP Troubleshooting — Read the scenario before looking for a memorised answer..

What is the correct answer to this question?

The correct answer is: The neighbor is configured with a distribute-list that filters all routes. — The scenario as described is internally inconsistent: if the interface facing the neighbor is configured as passive under the EIGRP process, the router stops sending hellos on that interface. Without receiving hellos from the local router, the neighbor adjacency would eventually fail. Since the adjacency is reported as up, the passive-interface configuration cannot be affecting this interface (or the adjacency would not be stable). Therefore, the passive-interface is not the issue. The most likely cause is that the neighbor has a distribute-list applied that filters all routes, preventing any routes from being advertised to the local router, even though the adjacency is established.

What should I do if I get this 300-410 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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