- A
The 'passive-interface' command also prevents EIGRP from sending routing updates on that interface.
Correct. The passive-interface command suppresses both hello packets and routing updates. Therefore, the remote sites do not receive the routes.
- B
The 'passive-interface' command only affects hello packets, not updates, but the remote sites are not configured correctly.
Why wrong: Incorrect. The passive-interface command suppresses both hello and update packets on the interface.
- C
The engineer should use the 'neighbor' command under the EIGRP process to specify the remote routers.
Why wrong: Incorrect. While the neighbor command can be used for static neighbors, it does not solve the issue of passive-interface blocking updates. The engineer would need to remove passive-interface or use a different method.
- D
The remote sites are using a different EIGRP autonomous system number.
Why wrong: Incorrect. If AS numbers differ, no adjacency would form, but the scenario says they were receiving routes before the passive-interface command.
Quick Answer
The answer is that the passive-interface command also prevents EIGRP from sending routing updates on that interface, which is why the remote sites stop receiving routes. In EIGRP, applying passive-interface suppresses both hello packets and routing updates, so while the router will still advertise the connected networks in theory, it cannot form or maintain neighbor adjacencies without those hellos. Without an adjacency, no route exchange occurs, leading to complete route loss for the remote sites. On the ENCOR 350-401 exam, this question tests your understanding that EIGRP’s passive-interface behaves differently from OSPF’s—in OSPF, it only suppresses hello packets but still allows route advertisement via existing adjacencies, whereas EIGRP blocks all outbound updates. A common trap is assuming the command only stops neighbor formation while leaving route propagation intact. Memory tip: for EIGRP, think “passive = silent on all fronts,” meaning no hellos and no updates.
CCNP EIGRP Practice Question
This 350-401 practice question tests your understanding of eigrp. Read the scenario carefully and evaluate each option against the stated constraints before committing to an answer. 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.
A network engineer is configuring EIGRP on a router that connects to multiple remote sites via Frame Relay. The engineer wants to ensure that EIGRP does not form adjacencies over the Frame Relay interfaces to reduce overhead, but still wants to advertise the connected networks. The engineer applies the 'passive-interface' command to the Frame Relay interfaces. However, the remote sites stop receiving the routes. What is the most likely reason?
Clue words in this question
Noticing these words before you look at the options changes how you read each choice.
Clue:
"most likely"Why it matters: Probability qualifier — the question wants the most probable cause or outcome, not a guaranteed one. Eliminate low-probability options.
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 'passive-interface' command also prevents EIGRP from sending routing updates on that interface.
The 'passive-interface' command in EIGRP prevents both hello and routing updates from being sent on the specified interface. Since EIGRP relies on hello packets to form and maintain neighbor adjacencies, applying this command to the Frame Relay interfaces stops adjacency formation. Without an adjacency, no routes are exchanged, so the remote sites stop receiving the advertised networks.
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 'passive-interface' command also prevents EIGRP from sending routing updates on that interface.
Why this is correct
Correct. The passive-interface command suppresses both hello packets and routing updates. Therefore, the remote sites do not receive the routes.
Clue confirmation
The clue word "most likely" in the question point toward this answer.
Related concept
Read the scenario before looking for a memorised answer.
- ✗
The 'passive-interface' command only affects hello packets, not updates, but the remote sites are not configured correctly.
Why it's wrong here
Incorrect. The passive-interface command suppresses both hello and update packets on the interface.
- ✗
The engineer should use the 'neighbor' command under the EIGRP process to specify the remote routers.
Why it's wrong here
Incorrect. While the neighbor command can be used for static neighbors, it does not solve the issue of passive-interface blocking updates. The engineer would need to remove passive-interface or use a different method.
- ✗
The remote sites are using a different EIGRP autonomous system number.
Why it's wrong here
Incorrect. If AS numbers differ, no adjacency would form, but the scenario says they were receiving routes before the passive-interface command.
Common exam traps
Common exam trap: answer the scenario, not the keyword
Cisco often tests the misconception that 'passive-interface' only affects routing updates but not hello packets, leading candidates to think adjacencies can still form and routes can be received.
Trap categories for this question
Command / output trap
Incorrect. The passive-interface command suppresses both hello and update packets on the interface.
Scenario analysis trap
Incorrect. If AS numbers differ, no adjacency would form, but the scenario says they were receiving routes before the passive-interface command.
Detailed technical explanation
How to think about this question
EIGRP uses multicast hello packets (224.0.0.10) to discover neighbors and maintain adjacencies. The 'passive-interface' command disables the sending of all EIGRP packets (hellos, updates, queries, replies) on that interface, effectively preventing any neighbor relationship from forming. In Frame Relay environments, this command is often misapplied because engineers forget that EIGRP requires a live adjacency to exchange routes, even if the interface is configured with static neighbors via the 'neighbor' command.
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 350-401 question test?
EIGRP — This question tests EIGRP — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: The 'passive-interface' command also prevents EIGRP from sending routing updates on that interface. — The 'passive-interface' command in EIGRP prevents both hello and routing updates from being sent on the specified interface. Since EIGRP relies on hello packets to form and maintain neighbor adjacencies, applying this command to the Frame Relay interfaces stops adjacency formation. Without an adjacency, no routes are exchanged, so the remote sites stop receiving the advertised networks.
What should I do if I get this 350-401 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: "most likely". Probability qualifier — the question wants the most probable cause or outcome, not a guaranteed one. Eliminate low-probability options.
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 350-401 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 350-401 exam.
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