Question 1,447 of 2,152

EIGRP Troubleshooting →easyMultiple ChoiceObjective-mapped

EIGRP Specific Route Missing: Distribute-List In

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 a specific route from a neighbor, but other routes from the same neighbor are being learned. The engineer checks the EIGRP topology table and sees that the route is not present. The engineer also checks the neighbor's routing table and confirms that the route exists. 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.

A
A distribute-list in is applied on the local router that filters the specific route.
Correct because a distribute-list can filter specific routes based on prefix or other criteria.
B
The neighbor is configured as a stub router.
Why wrong: Incorrect because a stub router would not advertise any routes except connected and summary, so all routes would be missing, not just one.
C
The route is a summary route that is being suppressed by the 'summary-address' command.
Why wrong: Incorrect because summary-address creates a summary route, it does not suppress a specific route.
D
The EIGRP metric for the route is too high, so it is not considered feasible.
Why wrong: Incorrect because if the route is not in the topology table at all, it is not being received, not that it is being ignored due to metric.

Full breakdown with real-world context →

Quick Answer

The answer is a distribute-list in applied on the local router that filters the specific route. This is correct because when only one EIGRP route is missing from a neighbor while all other routes from that same neighbor are learned successfully, the issue is almost always a targeted inbound filter. The distribute-list in command, often paired with an access-list or prefix-list, blocks only the matched prefix from entering the routing table, leaving the rest of the routes unaffected. On the Cisco CCNP ENARSI 300-410 exam, this scenario tests your ability to distinguish between global neighbor issues and route-specific filtering; a common trap is to assume the neighbor is not advertising the route, but the topology table confirms the route is absent only locally. A quick memory tip: if the route is missing from the topology table but present on the neighbor, think “filter in, not out”—the distribute-list in is blocking the inbound update.

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

✓

A distribute-list in is applied on the local router that filters the specific route.

A distribute-list in applied on the local router can filter specific incoming routes from an EIGRP neighbor while allowing others. Since the neighbor has the route in its routing table and other routes from the same neighbor are learned, the most likely cause is an inbound filter that explicitly denies that particular prefix.

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.

✓
A distribute-list in is applied on the local router that filters the specific route.
Why this is correct
Correct because a distribute-list can filter specific routes based on prefix or other criteria.
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 neighbor is configured as a stub router.
Why it's wrong here
Incorrect because a stub router would not advertise any routes except connected and summary, so all routes would be missing, not just one.
✗
The route is a summary route that is being suppressed by the 'summary-address' command.
Why it's wrong here
Incorrect because summary-address creates a summary route, it does not suppress a specific route.
✗
The EIGRP metric for the route is too high, so it is not considered feasible.
Why it's wrong here
Incorrect because if the route is not in the topology table at all, it is not being received, not that it is being ignored due to metric.

Common exam traps

Common exam trap: answer the scenario, not the keyword

Cisco often tests the distinction between inbound and outbound filtering, and candidates may mistakenly think a stub router or metric issue causes selective route absence, but only a distribute-list in can filter a single route from an otherwise fully functional neighbor relationship.

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. Inbound filtering (distribute-list in) is applied per interface and can selectively block specific prefixes while allowing others, which explains why only one route is missing from the topology table. This is a common troubleshooting scenario where the route is present in the neighbor's table but absent locally due to filtering.

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: A distribute-list in is applied on the local router that filters the specific route. — A distribute-list in applied on the local router can filter specific incoming routes from an EIGRP neighbor while allowing others. Since the neighbor has the route in its routing table and other routes from the same neighbor are learned, the most likely cause is an inbound filter that explicitly denies that particular prefix.

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.

About these practice questions

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Same concept, more angles

1 more ways this is tested on 300-410

These questions test the same concept from different angles. Work through them to make sure you can recognise it however the exam phrases it.

Variation 1. A network engineer is troubleshooting a routing issue in an EIGRP network. Router R1 is not learning a specific route from its neighbor R2, even though R2 has the route in its routing table. The engineer checks the EIGRP topology table on R1 and does not see the route. The output of 'show ip eigrp neighbors' shows that R1 and R2 are adjacent. What should the engineer check next?

medium

✓ A.Check if a distribute-list in or out is applied under the EIGRP process on R1.
B.Check if the route is being summarized on R2.
C.Check if the EIGRP metric for the route is too high.
D.Check if the route is a connected route on R2.

Why A: The correct answer is A because if R1 and R2 are EIGRP neighbors but R1 does not have the route in its topology table, a distribute-list applied inbound on R1 or outbound on R2 could be filtering the route. Distribute-lists use access-lists or prefix-lists to permit or deny routes during the update process, preventing specific routes from being installed in the topology table even though the neighbor adjacency is established.

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