hardMultiple Choice
300-410 Practice Question: An EIGRP network with multiple routers is…
An EIGRP network with multiple routers is experiencing frequent stuck-in-active (SIA) events for prefix 10.10.10.0/24. The network topology includes a slow WAN link between R1 and R2. R1's show ip eigrp topology 10.10.10.0/24 shows the route in active state with a query outstanding to R2. R2's show ip eigrp topology shows the same prefix in passive state. The EIGRP timers are default. What is the root cause?
⚠ Common exam trap
Cisco often tests the misconception that the SIA is caused by the directly connected slow link (between R1 and R2), when in fact the root cause is a slow link further downstream on R2, preventing R2 from replying in time.
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 a query outstanding to a neighbor over a slow link, preventing it from replying to R1 within the active timer.
R2 has the prefix in passive state, meaning it has not yet received a reply from one of its own neighbors over a slow link. Since R2 cannot reply to R1 until it gets that reply, R1's active timer expires, causing a stuck-in-active (SIA) event. This is a classic scenario where the query propagation delay exceeds the default active timer (3 minutes) due to a slow WAN link downstream from R2.
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 active timer on R1 is too short for the slow WAN link; it should be increased to accommodate query propagation delays.
Why it's wrong here
The active timer is not the root cause of the SIA; it is only the threshold that triggers the error. R1's timer is set to a default value and is designed to accommodate normal query propagation, so increasing it would merely hide the underlying issue. If R2 is genuinely stuck waiting on a downstream neighbor, a longer timer will not make that neighbor reply faster.
- ✓
R2 has a query outstanding to a neighbor over a slow link, preventing it from replying to R1 within the active timer.
Why this is correct
This is the classic SIA cause: R1 sends a query to R2 for the prefix, and R2 must propagate that query to all its neighbors and wait for every reply before it can formulate an answer to R1. If one of R2's downstream neighbors is over a slow or unreliable link and delays its reply, R2's response to R1 is held up beyond R1's active timer. That delay triggers the 'Stuck In Active' condition on R1.
- ✗
The EIGRP hello timer mismatch between R1 and R2 is causing neighbor flapping.
Why it's wrong here
EIGRP hello timers are not negotiated between neighbors; each router independently sends hello packets at its configured interval, and the hold time, not the hello time, determines adjacency loss. Even if R1 and R2 have different hello timers, as long as the hold time is greater than the hello interval, the neighbor relationship remains stable. SIA is caused by query/reply delays, not by hello timer mismatch, so this option does not explain the problem.
- ✗
The prefix 10.10.10.0/24 is being summarized, causing the query to be sent for the summary instead.
Why it's wrong here
EIGRP summarization affects which routes are advertised and how queries are scoped, but it does not by itself prevent a router from replying to a query. The question states that the specific prefix 10.10.10.0/24 is in active state, meaning the query is for that exact route, not a summary. If a summary were the issue, the active timer would be running for the summary route, not the specific prefix, so this does not align with the troubleshooting scenario.
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.
Go deeper
Related to this question
About these practice questions
This 300-410 question is part of Courseiva's 1,401-question bank — original exam-style content with full explanations and wrong-answer analysis, never real exam questions or exam dumps. Learn why practice questions differ from exam dumps →
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.