- A
The active timer on R1 is too short for the slow WAN link; it should be increased to accommodate query propagation delays.
Why wrong: Increasing the active timer may mask the issue but does not fix the root cause if the query is stuck due to a downstream neighbor.
- B
R2 has a query outstanding to a neighbor over a slow link, preventing it from replying to R1 within the active timer.
R2 cannot reply until it receives all replies to its own queries. If a downstream neighbor is slow or unresponsive, R2's reply to R1 is delayed, causing SIA.
- C
The EIGRP hello timer mismatch between R1 and R2 is causing neighbor flapping.
Why wrong: Hello timer mismatch does not cause SIA; it affects neighbor adjacency.
- D
The prefix 10.10.10.0/24 is being summarized, causing the query to be sent for the summary instead.
Why wrong: Summarization can cause SIA if the summary is not in the topology, but here the specific prefix is in active state.
Quick Answer
The answer is that the root cause is a query outstanding to a neighbor over a slow link downstream from R2. This is the classic EIGRP stuck-in-active cause: R2 has the prefix in passive state, meaning it has received R1’s query but cannot reply because it is still waiting for a reply from its own neighbor across a slow WAN link. Since EIGRP uses default active timers (3 minutes), the propagation delay through that slow link causes R1’s timer to expire before R2 can respond, triggering the SIA event. On the Cisco CCNP ENARSI 300-410 exam, this scenario tests your understanding of query propagation and the active timer’s role in preventing indefinite convergence delays. A common trap is assuming the slow link is directly between R1 and R2, but the key is that R2 is passive—it has already received the query and is waiting downstream. Memory tip: “Passive R2 means the bottleneck is beyond it—check the next hop’s slow link.”
300-410 Device Access Control Practice Question
This 300-410 practice question tests your understanding of device access control. The scenario asks you to isolate a root cause — eliminate options that address a different problem before choosing. After answering, compare your reasoning against the explanation and wrong-answer breakdown below. Once you have made your selection, read the full explanation to reinforce the concept and understand why each distractor is designed to mislead on exam day.
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?
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.
The correct answer is B because 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.
Key principle: Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
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
Increasing the active timer may mask the issue but does not fix the root cause if the query is stuck due to a downstream neighbor.
- ✓
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
R2 cannot reply until it receives all replies to its own queries. If a downstream neighbor is slow or unresponsive, R2's reply to R1 is delayed, causing SIA.
Related concept
Read the scenario before looking for a memorised answer.
- ✗
The EIGRP hello timer mismatch between R1 and R2 is causing neighbor flapping.
Why it's wrong here
Hello timer mismatch does not cause SIA; it affects neighbor adjacency.
- ✗
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
Summarization can cause SIA if the summary is not in the topology, but here the specific prefix is in active state.
Common exam traps
Common exam trap: answer the scenario, not the keyword
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.
Detailed technical explanation
How to think about this question
In EIGRP, when a router loses a route and has a feasible successor, it goes active and sends queries to all neighbors. The active timer (default 3 minutes) is the maximum time a router waits for all replies before declaring the route SIA. If a downstream router (R2) has the route passive but has sent queries to its own neighbors over a slow link, it cannot reply until it receives all replies, potentially exceeding the active timer. This cascading query propagation is a common cause of SIA in hub-and-spoke or WAN topologies, and can be mitigated by adjusting the active timer or using route summarization to limit query scope.
KKey Concepts to Remember
- Read the scenario before looking for a memorised answer.
- Find the constraint that changes the correct option.
- Eliminate answers that are true in general but not in this case.
TExam Day Tips
- Watch for words such as best, first, most likely and least administrative effort.
- Review why wrong options are wrong, not only why the correct option is correct.
Key takeaway
Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Real-world example
How this comes up in practice
A network engineer at a university connects two campus buildings via a fibre link. Both routers run OSPF, but no adjacency forms — even though both routers can ping each other. The engineer finds one router is in area 0 and the other in area 1. OSPF adjacency requires matching area numbers, hello/dead timers, and network type. IP reachability alone is not enough.
What to study next
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FAQ
Questions learners often ask
What does this 300-410 question test?
Device Access Control — This question tests Device Access Control — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: R2 has a query outstanding to a neighbor over a slow link, preventing it from replying to R1 within the active timer. — The correct answer is B because 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.
What should I do if I get this 300-410 question wrong?
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
What is the key concept behind this question?
Read the scenario before looking for a memorised answer.
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Last reviewed: Jun 24, 2026
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.
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