The answer is that the hub is not configured with NHRP redirect. In DMVPN Phase 3, spoke-to-spoke direct communication relies on the hub sending NHRP redirect messages to inform a spoke that a more direct path exists to another spoke’s tunnel IP. Without the hub’s NHRP redirect enabled, the spoke’s NHRP cache will only map the remote spoke’s tunnel IP to the hub’s physical IP, forcing all traffic through the hub rather than establishing a direct shortcut. On the ENCOR 350-401 exam, this scenario tests your understanding of the Phase 3 control-plane signaling difference: Phase 2 uses NHRP traffic indication, but Phase 3 requires the hub to actively redirect. A common trap is assuming spoke registration or routing protocol convergence alone enables direct tunnels—they do not. Remember the memory tip: “No redirect, no shortcut—traffic stays in the hub’s court.”
CCNP VPN Technologies Practice Question
This 350-401 practice question tests your understanding of vpn technologies. This is a configuration task: choose the command set that satisfies every stated requirement. Small differences — like 'secret' vs 'password' or 'transport input ssh' vs 'all' — change whether the answer is correct. 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 network. The hub router is a Cisco 4500X and the spokes are Cisco 4321s. The engineer wants to enable spoke-to-spoke direct communication. After configuration, the spokes can communicate via the hub, but not directly. The engineer checks the NHRP cache on a spoke and sees that it has a mapping for the other spoke's tunnel IP to the hub's physical IP. What is the most likely cause?
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 the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
The hub is not configured with NHRP redirect.
In DMVPN Phase 3, spokes must use NHRP redirect and shortcut routes to enable direct spoke-to-spoke communication. If the hub is not configured with the NHRP redirect feature, the spokes will not receive the redirect messages, and traffic will continue to go through the hub. Option C is correct because the hub must have NHRP redirect enabled. Option A is incorrect because the spokes are registered. Option B is incorrect because the routing protocol is working. Option D is incorrect because the tunnel mode is correct.
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 NHRP network ID is mismatched between the spokes.
Why it's wrong here
If the network ID mismatched, the spokes would not register.
✗
The routing protocol is not redistributing spoke routes.
Why it's wrong here
Routes are being exchanged because traffic flows via the hub.
✓
The hub is not configured with NHRP redirect.
Why this is correct
Correct because NHRP redirect is required for Phase 3 spoke-to-spoke shortcuts.
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 spokes are using GRE instead of mGRE.
Why it's wrong here
Spokes use GRE, which is correct for DMVPN.
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.
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.
VPN Technologies — This question tests VPN Technologies — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: The hub is not configured with NHRP redirect. — In DMVPN Phase 3, spokes must use NHRP redirect and shortcut routes to enable direct spoke-to-spoke communication. If the hub is not configured with the NHRP redirect feature, the spokes will not receive the redirect messages, and traffic will continue to go through the hub. Option C is correct because the hub must have NHRP redirect enabled. Option A is incorrect because the spokes are registered. Option B is incorrect because the routing protocol is working. Option D is incorrect because the tunnel mode is correct.
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.
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