hardMultiple ChoiceObjective-mapped
300-410 Practice Question: An engineer configures a DMVPN Phase 2 network
An engineer configures a DMVPN Phase 2 network. Spoke routers can communicate with the hub, but spoke-to-spoke traffic does not trigger a direct tunnel. Which is the most likely explanation?
⚠ Common exam trap
Cisco often tests the distinction between Phase 2 and Phase 3 DMVPN behaviors, and the trap here is that candidates confuse the spoke's 'ip nhrp shortcut' (which is required for Phase 2) with the hub's 'ip nhrp redirect' (which is also required), assuming that only one of them is necessary for spoke-to-spoke tunnels.
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 missing the 'ip nhrp redirect' command.
In a DMVPN Phase 2 network, spoke-to-spoke tunnels are triggered dynamically when a spoke receives an NHRP redirect from the hub. The 'ip nhrp redirect' command on the hub router enables it to send redirect messages to spokes, informing them of a more direct path to another spoke. Without this command, the hub forwards traffic between spokes but never signals the spokes to build a direct tunnel, so spoke-to-spoke traffic continues to traverse 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 hub router is missing the 'ip nhrp redirect' command.
Why this is correct
Correct. Redirect is required for Phase 2 spoke-to-spoke.
- ✗
The spoke routers have 'ip nhrp shortcut' configured.
Why it's wrong here
Shortcut is required on spokes; its presence would help, not hinder.
- ✗
The tunnel mode is set to gre multipoint on the spokes.
Why it's wrong here
GRE multipoint is correct for Phase 2.
- ✗
The NHRP authentication is mismatched.
Why it's wrong here
Authentication mismatch would prevent all NHRP communication.
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
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