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300-410 Practice Question: An engineer configures a DMVPN Phase 2 network
An engineer configures a DMVPN Phase 2 network. Spoke-to-spoke tunnels are not forming. Which is the most likely explanation?
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
✓
NHRP redirect is not configured on the hub.
In DMVPN Phase 2, spoke-to-spoke tunnels require that the spoke routers have a route to the destination network via the tunnel interface, and that NHRP redirect is enabled on the hub. Without NHRP redirect, the hub will not send redirect messages to the spoke, and the spoke will not initiate a direct tunnel to the other spoke.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✓
NHRP redirect is not configured on the hub.
Why this is correct
In Phase 2, the hub must send NHRP redirect messages to trigger spoke-to-spoke tunnel establishment. Without it, traffic will always go through the hub.
- ✗
The spoke routers have different tunnel keys.
Why it's wrong here
Tunnel keys must match for the tunnel to form, but this would affect the initial tunnel establishment, not specifically spoke-to-spoke.
- ✗
The NHRP authentication string is mismatched.
Why it's wrong here
Mismatched authentication would prevent NHRP registration, not specifically spoke-to-spoke tunnels.
- ✗
The IPsec transform-set is mismatched.
Why it's wrong here
IPsec transform-set mismatch would affect the IPsec SA, not the NHRP-driven spoke-to-spoke tunnel establishment.
Go deeper
Related to this question
Learn chapter
Introduction to ENARSI Exam and Network Fundamentals
Key term
DMVPN Phase 2
DMVPN Phase 2 is an advanced Cisco routing technology that allows spoke routers to communicate directly with one another without sending traffic through a central hub, using dynamic routing protocols and multipoint GRE tunnels.
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JA
Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
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.