mediumMultiple ChoiceObjective-mapped
300-410 Practice Question: An engineer is troubleshooting a DMVPN phase 2…
An engineer is troubleshooting a DMVPN phase 2 network where the hub router is not forming an EIGRP neighbor relationship with a spoke. The spoke's tunnel interface is configured with 'ip nhrp nhs 10.0.0.1' and 'ip nhrp map 10.0.0.1 192.168.1.1'. The hub's tunnel interface IP is 10.0.0.1. The engineer pings the hub's tunnel IP from the spoke and it succeeds. The engineer checks 'show ip eigrp neighbors' on the hub and sees no neighbors. What is the most likely cause?
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 spoke's tunnel interface is missing the 'ip nhrp map multicast dynamic' command.
EIGRP neighbor formation over a tunnel requires multicast support. In DMVPN, multicast traffic is sent via NHRP to the hub. If the spoke's tunnel interface does not have 'ip nhrp map multicast dynamic' or a static multicast map, the hub will not receive EIGRP hello packets from the 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.
- ✓
The spoke's tunnel interface is missing the 'ip nhrp map multicast dynamic' command.
Why this is correct
Correct because without multicast mapping, the spoke cannot send multicast traffic (including EIGRP hellos) to the hub.
- ✗
The hub's tunnel interface has 'no ip nhrp redirect' configured.
Why it's wrong here
Incorrect because redirect is for spoke-to-spoke traffic, not for multicast.
- ✗
The spoke's EIGRP AS number does not match the hub's.
Why it's wrong here
Incorrect because AS mismatch would prevent neighbor formation, but the engineer would check that first.
- ✗
The hub's tunnel interface has 'ip nhrp authentication' configured but the spoke does not.
Why it's wrong here
Incorrect because NHRP authentication affects NHRP registration, not EIGRP neighbor formation.
Quick reference
Routing Protocol Comparison
| Protocol | Metric | Max Hops | Algorithm | Type |
|---|---|---|---|---|
| RIP v2 | Hop count | 15 | Bellman-Ford | Distance vector |
| OSPF | Cost (bandwidth) | Unlimited | Dijkstra (SPF) | Link state |
| EIGRP | Composite metric | Unlimited | DUAL | Hybrid |
| IS-IS | Cost | Unlimited | Dijkstra | Link state |
| BGP | Policy / attributes | Unlimited | Path vector | Path vector |
RIP's 15-hop limit makes it unsuitable for large networks. OSPF and EIGRP dominate modern enterprise deployments.
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.