hardMultiple Select
EIGRP Routes in Topology But Not Routing Table: Common Causes
An engineer is troubleshooting an EIGRP network where routes from router R1 are not being installed in the routing table of router R2, although R2 sees them in the EIGRP topology table. Which TWO configuration issues could cause this problem? (Choose TWO.)
Quick Answer
The answer is that an offset-list configured on R2 increasing the metric by 1000, or an administrative distance mismatch from another routing protocol, can cause EIGRP routes to appear in the topology table but not the routing table. The offset-list artificially inflates the composite metric, making the route less preferred than a lower-metric path from another neighbor, while a higher administrative distance (e.g., from a static route or another dynamic protocol) can prevent the EIGRP route from being installed even if it is the best metric. On the Cisco CCNP ENARSI 300-410 exam, this scenario tests your understanding of the EIGRP route selection process—specifically that the topology table holds all feasible successors, but only the best metric route with the lowest AD gets into the routing table. A common trap is confusing the variance or maximum-paths commands with route installation; variance only affects load balancing, not whether a single route is installed. Memory tip: “Topology shows the options, but AD and metric decide the insertion.”
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
✓
R2 has an OSPF route with administrative distance 110 for the same prefix, and the EIGRP route is external with administrative distance 170.
Option B is correct because EIGRP external routes have a default administrative distance of 170, which is higher (less preferred) than OSPF's 110, so R2 would keep the OSPF route in the routing table even though the EIGRP route appears in the topology table. Option D is correct because an offset-list applied to EIGRP increments the reported/advertised metric for matching routes, and if that inflated metric makes the path from R1 worse than an alternate path from another neighbor, R2 will not install the R1 route as the best route. Option A is not correct because a static route with AD 150 is less preferred than EIGRP's internal AD of 90, so EIGRP would still win and be installed. Option C is not correct because variance only enables unequal-cost load balancing via feasible successors; a higher-metric feasible successor not being used does not prevent the successor route itself from being installed. Option E is not correct because maximum-paths limits how many equal-cost paths are installed, but it does not prevent the first/best EIGRP route for a prefix from being placed in the routing table.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
R2 has a static route with administrative distance 150 for the same prefix, and EIGRP's default administrative distance is 90.
Why it's wrong here
A static route with administrative distance 150 is less preferred than EIGRP internal (AD 90), so it does not prevent the EIGRP route from being installed. This does not cause the problem.
- ✓
R2 has an OSPF route with administrative distance 110 for the same prefix, and the EIGRP route is external with administrative distance 170.
Why this is correct
EIGRP external routes carry administrative distance 170, higher than OSPF's 110. When both protocols offer the same prefix, the router installs the lower-distance OSPF route, so the EIGRP entry stays in the topology table but never enters the routing table.
- ✗
The 'variance' command is configured on R2 with a value of 2, but the EIGRP route has a feasible successor with a higher metric.
Why it's wrong here
The 'variance' command allows multiple unequal-cost paths but does not affect whether the best route is installed; the route is still installed if it is the best path. This does not cause the problem.
- ✓
R2 has an 'offset-list' configured that increases the metric of the route from R1 by 1000, making it less preferred than a route from another neighbor.
Why this is correct
An offset-list applied inbound on R2 adds 1000 to the metric of routes from R1, raising the composite metric above a competing neighbour's route. The prefix stays in the topology table but loses the best-path selection, so it is not installed.
- ✗
The 'maximum-paths' command on R2 is set to 1, and there is already one EIGRP route for the same prefix in the routing table.
Why it's wrong here
The 'maximum-paths' command limits the number of equal-cost paths; if only one path is allowed, a second route with a higher metric would not be installed anyway due to metric comparison, not due to maximum-paths. This does not cause the problem.
Visual reference
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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Same concept, more angles
1 more way 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 an EIGRP issue where a router is not installing a route in the routing table, even though the route is present in the EIGRP topology table. The route is a feasible successor, but it is not being used. What is the most likely reason for this?
medium- ✓ A.The feasible successor has a higher metric than the current successor.
- B.The route is a summary route that is being suppressed.
- C.The route is being filtered by a distribute-list in.
- D.The EIGRP variance command is set to 1, preventing unequal-cost load balancing.
Why A: In EIGRP, a feasible successor is a backup route that meets the feasibility condition (reported distance < feasible distance). However, the router will only install the route with the best metric (the successor) into the routing table. If the feasible successor has a higher metric than the current successor, it will remain in the topology table as a backup but will not be used unless the successor fails. This matches option A.
JA
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.