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300-410 Practice Question: In a DMVPN Phase 2 network with EIGRP, R1 (hub)…
In a DMVPN Phase 2 network with EIGRP, R1 (hub) and R2 (spoke) are configured. R2's tunnel interface has an ACL applied inbound that denies ICMP. R2 can ping R1's tunnel IP, but R1 cannot ping R2's tunnel IP. What is the root 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
✓
R2's tunnel interface has an inbound ACL that denies ICMP, blocking R1's ping requests.
The ACL on R2's tunnel interface inbound denies ICMP. When R1 sends an ICMP echo request to R2, it is denied by the ACL. However, R2 can ping R1 because the ACL does not affect outbound traffic. The issue is that the ACL is applied inbound, blocking incoming ICMP packets.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✓
R2's tunnel interface has an inbound ACL that denies ICMP, blocking R1's ping requests.
Why this is correct
Correct. Inbound ACLs filter traffic entering the interface. ICMP echo requests from R1 are denied, so R1 cannot ping R2.
- ✗
R1's tunnel interface has an outbound ACL that denies ICMP.
Why it's wrong here
Incorrect. An outbound ACL on R1 would block traffic leaving R1, but R2 can ping R1, so outbound traffic is not blocked.
- ✗
NHRP is not resolving R2's tunnel IP to its physical IP on R1.
Why it's wrong here
Incorrect. If R2 can ping R1, NHRP resolution is working.
- ✗
EIGRP is not advertising R2's tunnel IP to R1.
Why it's wrong here
Incorrect. R2 can ping R1, so routing is working.
Visual reference
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.