mediumMultiple Choice
300-410 Practice Question: Consider the following partial DMVPN…
Consider the following partial DMVPN configuration on a hub router:
interface Tunnel0 ip address 10.0.0.1 255.255.255.0 ip nhrp network-id 100 ip nhrp authentication cisco123
tunnel source GigabitEthernet0/0 tunnel mode gre multipoint
ip nhrp map multicast dynamic
!
What is the effect of this configuration?
⚠ Common exam trap
300-410 often tests the confusion between static and dynamic multicast mapping in DMVPN, leading candidates to think dynamic mapping is not supported or requires static entries.
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 will dynamically register spoke NHRP addresses and forward multicast traffic to all registered spokes.
The command 'ip nhrp map multicast dynamic' on the hub allows the hub to dynamically learn the multicast mapping for spokes. This means the hub will forward multicast traffic to all registered spokes that have registered via NHRP. The hub does not require static multicast mappings for each spoke. This is essential for DMVPN phase 2 and 3 where dynamic routing protocols use multicast.
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 will dynamically register spoke NHRP addresses and forward multicast traffic to all registered spokes.
Why this is correct
The ip nhrp map multicast dynamic command lets the hub learn spoke NBMA addresses from registration requests and replicate multicast or broadcast traffic to every registered spoke, while tunnel mode gre multipoint provides the single multipoint GRE interface spokes register against.
- ✗
The hub will only forward multicast traffic to spokes that are statically mapped.
Why it's wrong here
The ip nhrp map multicast dynamic command lets the hub dynamically learn spoke NBMA addresses for multicast, so static mapping is unnecessary. Static mapping is tempting because it was required in older DMVPN designs without this command.
- ✗
The hub will not forward multicast traffic at all because dynamic mapping is not supported.
Why it's wrong here
Dynamic multicast mapping is supported and enabled by the `ip nhrp map multicast dynamic` command, so the hub does forward multicast to registered spokes. The option is tempting because NHRP multicast maps normally require static entries per spoke; dynamic mapping removes that manual step, which is exactly what this configuration achieves.
- ✗
The hub will use broadcast instead of multicast for all traffic.
Why it's wrong here
Broadcast is not substituted for multicast by any command here; `ip nhrp map multicast dynamic` makes the hub replicate multicast and broadcast packets to all registered spokes, so multicast transport remains. The option tempts those who conflate NHRP multicast mapping with broadcast forwarding, which would apply only where multicast replication across the tunnel is deliberately disabled.
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
ACL-Based Traffic Filtering and Policy-Based Routing
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 and reviewed by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
Last reviewed September 2026 · checked against the official Cisco exam blueprint
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.