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300-410 Practice Question: Is troubleshooting an EIGRP issue where a router…
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?
⚠ Common exam trap
Cisco often tests the distinction between a route being present in the topology table versus being installed in the routing table, tricking candidates into thinking that any feasible successor should be used immediately, when in fact only the successor (lowest metric) is installed by default.
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 feasible successor has a higher metric than the current successor.
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.
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 feasible successor has a higher metric than the current successor.
Why this is correct
Correct because EIGRP installs only the route with the lowest metric (successor) into the routing table; feasible successors are kept as backup routes.
- ✗
The route is a summary route that is being suppressed.
Why it's wrong here
Incorrect because summary routes are installed in the routing table if they are the best path.
- ✗
The route is being filtered by a distribute-list in.
Why it's wrong here
Incorrect because if a route is in the topology table, it has not been filtered by a distribute-list in.
- ✗
The EIGRP variance command is set to 1, preventing unequal-cost load balancing.
Why it's wrong here
Incorrect because variance only affects whether feasible successors are used for load balancing; it does not prevent the successor from being installed.
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.