hardMultiple ChoiceObjective-mapped
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 expected to form dynamically. However, when a spoke tries to reach another spoke, traffic is still sent through the hub. The engineer verifies that NHRP is working and that the spoke-to-spoke tunnel is up. 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
✓
The spokes are missing the 'ip nhrp shortcut' command on the tunnel interface, so they do not install the direct route.
In DMVPN Phase 2, spoke-to-spoke tunnels require that the spokes have a direct route to each other's tunnel IP addresses. This is achieved through NHRP redirect and shortcut routes. However, a common edge case is that the spoke routers are configured with 'ip nhrp redirect' on the hub but the spokes are missing 'ip nhrp shortcut' on their tunnel interfaces. Without the shortcut command, the spoke will not install the NHRP-learned route into the routing table, so traffic continues to go through the hub.
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 spokes are missing the 'ip nhrp shortcut' command on the tunnel interface, so they do not install the direct route.
Why this is correct
The 'ip nhrp shortcut' command is required on spokes to allow them to use the NHRP-learned direct path. Without it, the spoke will continue to use the hub as the next hop.
- ✗
The hub is configured with 'ip nhrp redirect' but the spokes are configured with 'ip nhrp server-only', which prevents them from sending redirects.
Why it's wrong here
Spokes do not need to send redirects; they need to receive them. The 'server-only' command is for hubs, not spokes.
- ✗
The tunnel interface has 'ip mtu' set too low, causing fragmentation and preventing the NHRP registration.
Why it's wrong here
NHRP registration uses small packets and is not typically affected by MTU. The scenario states NHRP is working.
- ✗
The spoke-to-spoke tunnel uses IPsec, and the transform set is mismatched, causing the tunnel to fail.
Why it's wrong here
The scenario states the spoke-to-spoke tunnel is up, so IPsec is working.
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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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.