hardMultiple ChoiceObjective-mapped
300-410 DMVPN network with hub R1 and spoke R2 Practice Question
DMVPN network with hub R1 and spoke R2. R1 has:
interface Tunnel0 ip address 172.16.1.1 255.255.255.0
tunnel source GigabitEthernet0/0 tunnel mode gre multipoint
ip nhrp network-id 1 ip nhrp authentication cisco123
R2 has:
interface Tunnel0 ip address 172.16.1.2 255.255.255.0
tunnel source GigabitEthernet0/0 tunnel mode gre multipoint
ip nhrp network-id 1 ip nhrp nhs 172.16.1.1 ip nhrp authentication cisco123
R2 shows:
R2# show dmvpn
Legend: Attrb -> S: Static, D: Dynamic, I: Incomplete NHRP domain: 1
Interface: Tunnel0, IPv4 NHRP Details
Type:Spoke, NHC:172.16.1.2, NBMA:10.2.2.2 (no NHRP mappings)
R2# ping 172.16.1.1 source 172.16.1.2
Type escape sequence to abort. Sending 5, 100-byte ICMP Echos to 172.16.1.1, timeout is 2 seconds: ..... Success rate is 0 percent (0/5) 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
✓
The hub R1 is missing the 'ip nhrp map multicast dynamic' command.
The NHRP authentication strings do not match: R1 has 'cisco123', R2 has 'cisco123'? They match. But the output shows no NHRP mappings. The issue is that the spoke R2 has not registered with the hub. This could be due to a mismatch in NHRP network ID, but they match. Another possibility is that the hub's tunnel interface is not configured with 'ip nhrp map multicast dynamic' to accept registrations. Without that, the hub does not add the spoke to its NHRP database, and the spoke cannot resolve the hub's NBMA address. The ping fails because the spoke has no NHRP mapping for 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 R1 is missing the 'ip nhrp map multicast dynamic' command.
Why this is correct
Without this command, the hub does not accept NHRP registrations from spokes, so the spoke cannot build a mapping.
- ✗
The authentication string is mismatched between hub and spoke.
Why it's wrong here
Both have 'cisco123'.
- ✗
The tunnel mode on R2 should be 'tunnel mode gre ip' instead of multipoint.
Why it's wrong here
Spokes can use multipoint or point-to-point; multipoint is fine.
- ✗
The NHRP network ID must be different on hub and spoke.
Why it's wrong here
Network IDs must match.
Visual reference
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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.