mediumMultiple ChoiceObjective-mapped
300-410 Practice Question: An engineer is troubleshooting an EIGRP issue…
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?
⚠ Common exam trap
Cisco often tests the distinction between conditions that prevent adjacency formation (like mismatched K values or AS numbers) versus conditions that allow adjacency but suppress route advertisement (like stub configuration), leading candidates to incorrectly select metric weight mismatches when the adjacency is already up.
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.
When an EIGRP neighbor adjacency is up but no routes are received from the neighbor, the most likely cause is that the neighbor is configured as an EIGRP stub router. A stub router advertises only a default route or its directly connected and summary routes, depending on the stub setting, and does not advertise all learned routes. Since the engineer confirmed the neighbor has routes to advertise, the stub configuration on the neighbor would prevent those routes from being sent, even though the adjacency remains established.
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.
- ✗
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.
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.
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Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
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