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300-410 Practice Question: EIGRP network is experiencing stuck-in-active…
EIGRP network is experiencing stuck-in-active (SIA) routes. Router R1 shows: show ip eigrp topology active includes 10.0.0.0/24. Router R2 has: interface GigabitEthernet0/0, ip summary-address eigrp 100 10.0.0.0 255.255.255.0. What is the root cause?
⚠ Common exam trap
Cisco often tests the subtle interaction between EIGRP summary addresses and query suppression, where candidates mistakenly think SIA is caused by flapping or interface issues, rather than understanding that a summary address on a downstream router can prevent query replies for more specific prefixes.
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 summary address on R2 is causing a query for the specific route to be suppressed.
The summary address configured on R2 (ip summary-address eigrp 100 10.0.0.0 255.255.255.0) causes R2 to advertise a single summary route (10.0.0.0/24) to R1. When R1 loses its route to 10.0.0.0/24 and sends a query for the specific prefix, R2 does not reply because the summary address suppresses the query for the more specific route, leaving R1 stuck-in-active (SIA) waiting for a reply that never comes.
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 summary address on R2 is causing a query for the specific route to be suppressed.
Why this is correct
Summary addresses can cause queries to be aggregated, leading to SIA if replies are not received.
- ✗
R1 has a stuck interface causing the SIA.
Why it's wrong here
SIA is due to query/reply issues, not interface state.
- ✗
EIGRP is misconfigured with wrong autonomous system number.
Why it's wrong here
AS number mismatch would prevent neighbor formation.
- ✗
The route 10.0.0.0/24 is flapping, causing continuous queries.
Why it's wrong here
Flapping can cause SIA, but the summary is the direct cause here.
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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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.