- A
The hub router is configured with 'no ip next-hop-self eigrp' under the tunnel interface.
Why wrong: Incorrect because disabling next-hop-self would actually help spokes learn the real next hop of remote spokes. The issue is that next-hop-self is still enabled, causing spokes to see the hub as the next hop.
- B
The hub router is configured with 'ip next-hop-self eigrp' under the tunnel interface.
Correct. With next-hop-self enabled, the hub advertises routes with its own IP as the next hop, preventing spokes from learning the remote spoke's tunnel IP and thus no direct tunnel is built.
- C
The spoke routers have 'ip nhrp shortcut' configured but the hub does not have 'ip nhrp redirect'.
Why wrong: Incorrect. NHRP redirect is used on the hub to inform spokes that a better path exists. Without it, spokes may still forward through the hub, but the primary cause here is the next-hop-self behavior in EIGRP.
- D
The spoke routers are using static NHRP mappings to the hub only, without dynamic NHRP registration.
Why wrong: Incorrect. Dynamic NHRP registration is needed for spokes to learn each other, but the scenario describes correct NHRP and mGRE configuration. The routing protocol's next-hop behavior is the key issue.
Quick Answer
The answer is the hub router configured with 'ip next-hop-self eigrp' under the tunnel interface. In DMVPN Phase 3, spoke-to-spoke traffic relies on NHRP redirect messages from the hub to inform spokes of a remote spoke’s real next-hop IP, allowing them to install a direct shortcut. When the hub applies next-hop-self in its EIGRP updates, spokes learn the hub’s tunnel IP as the next hop for all remote networks, forcing traffic through the hub instead of establishing a direct spoke-to-spoke tunnel. On the ENCOR 350-401 exam, this tests your understanding of the critical interplay between NHRP redirect and routing protocol behavior in Phase 3—a common trap is assuming correct mGRE and NHRP configuration alone guarantees direct spoke communication. Remember the key: Phase 3 requires the hub to disable next-hop-self so spokes see the true next hop and trigger the NHRP shortcut. Memory tip: “Phase 3 needs the hub to be selfless—no next-hop-self.”
350-401 WAN Technologies Practice Question
This 350-401 practice question tests your understanding of wan technologies. 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.
A network engineer is configuring a DMVPN Phase 3 deployment with EIGRP as the routing protocol. The hub router has multiple spoke routers behind a single physical interface. The engineer notices that spoke-to-spoke traffic is being forwarded through the hub instead of directly. The spoke routers have the correct NHRP and mGRE configuration. What is the most likely cause of this issue?
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 hub router is configured with 'ip next-hop-self eigrp' under the tunnel interface.
In DMVPN Phase 3, spoke-to-spoke tunnels require NHRP redirect and routing protocol next-hop-self behavior to be disabled on the hub so that spokes learn the remote spoke's next-hop IP and install a direct NHRP shortcut. If the hub still sets next-hop-self in EIGRP updates, spokes will see the hub as the next hop and forward traffic through it.
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 hub router is configured with 'no ip next-hop-self eigrp' under the tunnel interface.
Why it's wrong here
Incorrect because disabling next-hop-self would actually help spokes learn the real next hop of remote spokes. The issue is that next-hop-self is still enabled, causing spokes to see the hub as the next hop.
- ✓
The hub router is configured with 'ip next-hop-self eigrp' under the tunnel interface.
Why this is correct
Correct. With next-hop-self enabled, the hub advertises routes with its own IP as the next hop, preventing spokes from learning the remote spoke's tunnel IP and thus no direct tunnel is built.
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 spoke routers have 'ip nhrp shortcut' configured but the hub does not have 'ip nhrp redirect'.
Why it's wrong here
Incorrect. NHRP redirect is used on the hub to inform spokes that a better path exists. Without it, spokes may still forward through the hub, but the primary cause here is the next-hop-self behavior in EIGRP.
- ✗
The spoke routers are using static NHRP mappings to the hub only, without dynamic NHRP registration.
Why it's wrong here
Incorrect. Dynamic NHRP registration is needed for spokes to learn each other, but the scenario describes correct NHRP and mGRE configuration. The routing protocol's next-hop behavior is the key issue.
Common exam traps
Common exam trap: answer the scenario, not the keyword
Many certification questions include familiar terms but test a specific constraint. Read the exact wording before choosing an answer that is generally true but wrong for this case.
Trap categories for this question
Scenario analysis trap
Incorrect. Dynamic NHRP registration is needed for spokes to learn each other, but the scenario describes correct NHRP and mGRE configuration. The routing protocol's next-hop behavior is the key issue.
Detailed technical explanation
How to think about this question
This question should be treated as a scenario, not a definition check. Identify the problem, the constraint and the best action. Then compare each option against those facts.
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.
- Use explanations to understand the rule behind the answer.
TExam Day Tips
- Underline the problem statement mentally.
- 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 350-401 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 350-401 exam domain this question belongs to, then review the specific concept being tested. Practise related questions in that domain and focus on understanding why each wrong answer is tempting — not just why the correct answer is right.
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FAQ
Questions learners often ask
What does this 350-401 question test?
WAN Technologies — This question tests WAN Technologies — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: The hub router is configured with 'ip next-hop-self eigrp' under the tunnel interface. — In DMVPN Phase 3, spoke-to-spoke tunnels require NHRP redirect and routing protocol next-hop-self behavior to be disabled on the hub so that spokes learn the remote spoke's next-hop IP and install a direct NHRP shortcut. If the hub still sets next-hop-self in EIGRP updates, spokes will see the hub as the next hop and forward traffic through it.
What should I do if I get this 350-401 question wrong?
Identify which 350-401 exam domain this question belongs to, then review the specific concept being tested. Practise related questions in that domain and focus on understanding why each wrong answer is tempting — not just why the correct answer is right.
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.
About these practice questions
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Last reviewed: Jun 18, 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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