easyMultiple Choice
300-410 Practice Question: An engineer is troubleshooting an EIGRP issue…
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?
⚠ Common exam trap
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.
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.
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
An inbound distribute-list filters routes before they enter the local EIGRP topology table, so the prefix is silently dropped while other routes from the same neighbour pass. The neighbour's own routing table still holds the route, matching the observed asymmetry.
- ✗
The neighbor is configured as a stub router.
Why it's wrong here
A stub router advertises only connected, summary, and redistributed routes, so a specific route present in its routing table but not redistributed is never advertised. It is tempting because stub routers do suppress routes, but they still advertise connected and summary routes, so other learned routes would also be missing.
- ✗
The route is a summary route that is being suppressed by the 'summary-address' command.
Why it's wrong here
The summary-address command creates summaries on the advertising router; it does not suppress a specific prefix the neighbour already has in its routing table. Summarisation is relevant when a component route is hidden behind an aggregate, not when the exact route is absent.
- ✗
The EIGRP metric for the route is too high, so it is not considered feasible.
Why it's wrong here
EIGRP installs any route with a finite metric as feasible; an excessively high metric still appears in the topology table as a feasible successor or successor. Metric values govern path selection, not whether a route is learned at all.
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
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.