- A
R1's distribute-list out under EIGRP is filtering the prefix 192.168.1.0/24 from being advertised to R2.
The distribute-list out on R1 prevents the prefix from being sent to R2, so R2 never receives the route and the prefix stays in active state.
- B
EIGRP split-horizon is enabled on the tunnel interface.
Why wrong: Split-horizon would prevent R1 from advertising routes learned from R2 back to R2, but this is a locally originated route.
- C
The IPsec tunnel is dropping EIGRP multicast packets.
Why wrong: If IPsec dropped multicast, EIGRP adjacency would fail entirely, but R2 sees the prefix as active, indicating adjacency is up.
- D
R2 has a passive interface configured for the tunnel.
Why wrong: A passive interface on R2 would prevent R2 from sending hellos, but adjacency would not form; the symptom shows adjacency exists.
Quick Answer
The answer is R1’s distribute-list out under EIGRP filtering the prefix 192.168.1.0/24 from being advertised to R2 over the IPsec tunnel. This command prevents the prefix from being included in EIGRP updates sent out the specified interface, so R2 never receives a reply to its query for that route, leaving it stuck in an active state and never transitioning to passive. On the Cisco CCNP ENARSI 300-410 exam, this scenario tests your understanding of how EIGRP distribute-list out interacts with route advertisement over a tunnel interface, especially in an IPsec site-to-site VPN context where the tunnel is the logical path. A common trap is assuming the tunnel itself is broken or that authentication is failing, when the real issue is a one-way filter blocking the update. Remember: if a route stays active on the neighbor, check the outbound filter on the advertising router first—distribute-list out blocks the update, not the query.
300-410 IPsec Site-to-Site VPN Practice Question
This 300-410 practice question tests your understanding of ipsec site-to-site vpn. Examine the command output carefully: the correct answer depends on what the output actually shows, not on general recall alone. 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.
R1 and R2 are running EIGRP with IPsec site-to-site VPN over a WAN link. The tunnel interface is used for the VPN. R1's EIGRP configuration includes a distribute-list out that filters prefix 192.168.1.0/24. R2's show ip eigrp topology shows the prefix as active but never transitions to passive. R2's show ip route does not have 192.168.1.0/24. What is the root cause?
Clue words in this question
Noticing these words before you look at the options changes how you read each choice.
Clue:
"never"Why it matters: Absolute qualifier. True only if the statement has zero exceptions — be cautious of options that seem obvious but break down in edge cases.
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
R1's distribute-list out under EIGRP is filtering the prefix 192.168.1.0/24 from being advertised to R2.
The distribute-list out command on R1 filters the prefix 192.168.1.0/24 from being included in EIGRP updates sent to R2. Since R2 never receives the route, it remains in an active state (query state) because it is still waiting for a reply from R1, and it never transitions to passive. This directly explains why the prefix is missing from R2's routing table.
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.
- ✓
R1's distribute-list out under EIGRP is filtering the prefix 192.168.1.0/24 from being advertised to R2.
Why this is correct
The distribute-list out on R1 prevents the prefix from being sent to R2, so R2 never receives the route and the prefix stays in active state.
Clue confirmation
The clue word "never" in the question point toward this answer.
Related concept
Read the scenario before looking for a memorised answer.
- ✗
EIGRP split-horizon is enabled on the tunnel interface.
Why it's wrong here
Split-horizon would prevent R1 from advertising routes learned from R2 back to R2, but this is a locally originated route.
- ✗
The IPsec tunnel is dropping EIGRP multicast packets.
- ✗
R2 has a passive interface configured for the tunnel.
Why it's wrong here
A passive interface on R2 would prevent R2 from sending hellos, but adjacency would not form; the symptom shows adjacency exists.
Common exam traps
Common exam trap: answer the scenario, not the keyword
Cisco often tests the distinction between a route being filtered out (distribute-list) versus a neighbor relationship failing (passive interface or multicast drop), leading candidates to incorrectly attribute the active state to connectivity issues rather than a route advertisement filter.
Trap categories for this question
Command / output trap
A passive interface on R2 would prevent R2 from sending hellos, but adjacency would not form; the symptom shows adjacency exists.
Detailed technical explanation
How to think about this question
EIGRP uses a reliable transport protocol (RTP) for updates, queries, and replies. When a distribute-list out filters a prefix, the router never includes it in the update packet, so the neighbor never learns it. The active state in the topology table indicates that R2 has sent a query for the prefix and is waiting for a reply from R1; since R1 has no route to advertise (due to the filter), it may reply with an unreachable condition, but if the filter is applied after the query is sent, R1 might not reply correctly, leaving the route stuck in active state. In real-world scenarios, this often occurs when distribute-lists are misconfigured on hub routers in DMVPN or site-to-site VPNs, causing partial routing tables and blackholing traffic.
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 practitioner preparing for the 300-410 exam encounters this exact type of scenario on the job. The correct answer here is not the most general option — it is the best answer for the specific constraint described. Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option. Real exam questions reward reading the full scenario before eliminating options, because the constraint defines which answer fits.
What to study next
Got this wrong? Here's your next step.
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
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IPsec Site-to-Site VPN — study guide chapter
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FAQ
Questions learners often ask
What does this 300-410 question test?
IPsec Site-to-Site VPN — This question tests IPsec Site-to-Site VPN — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: R1's distribute-list out under EIGRP is filtering the prefix 192.168.1.0/24 from being advertised to R2. — The distribute-list out command on R1 filters the prefix 192.168.1.0/24 from being included in EIGRP updates sent to R2. Since R2 never receives the route, it remains in an active state (query state) because it is still waiting for a reply from R1, and it never transitions to passive. This directly explains why the prefix is missing from R2's routing table.
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.
Are there clue words in this question I should notice?
Yes — watch for: "never". Absolute qualifier. True only if the statement has zero exceptions — be cautious of options that seem obvious but break down in edge cases.
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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