The correct answer is that the hub will dynamically register spoke NHRP addresses and forward multicast traffic to all registered spokes. This command, ip nhrp map multicast dynamic, is essential because it enables the hub to automatically learn the public addresses of spokes as they register via NHRP, then use those mappings to replicate multicast traffic—such as EIGRP or OSPF hellos—to every spoke without requiring static multicast mappings. On the Cisco CCNP ENARSI 300-410 exam, this tests your understanding of DMVPN phase 2 or 3 hub configuration, where dynamic multicast replication is critical for routing protocol convergence. A common trap is confusing this with the static ip nhrp map multicast command, which requires manual spoke entries; dynamic is the only option that scales. Memory tip: think “dynamic = discover and distribute”—the hub discovers spokes and distributes multicast automatically.
300-410 DMVPN Practice Question
This 300-410 practice question tests your understanding of dmvpn. This is a configuration task: choose the command set that satisfies every stated requirement. Small differences — like 'secret' vs 'password' or 'transport input ssh' vs 'all' — change whether the answer is correct. After answering, compare your reasoning against the explanation and wrong-answer breakdown below. Once you have made your selection, read the full explanation to reinforce the concept and understand why each distractor is designed to mislead on exam day.
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
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' allows the hub to dynamically learn spoke NHRP addresses for multicast replication, which is essential for routing protocols (e.g., EIGRP, OSPF) that use multicast.
Key principle: OSPF neighbour adjacency depends on matching area, hello/dead timers, network type, and authentication — IP reachability alone is not enough.
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
This is correct; dynamic multicast mapping enables the hub to forward multicast to all spokes that have registered with NHRP.
The hub will only forward multicast traffic to spokes that are statically mapped.
Why it's wrong here
Dynamic mapping allows automatic forwarding to all registered spokes without static maps.
✗
The hub will not forward multicast traffic at all because dynamic mapping is not supported.
Why it's wrong here
Dynamic mapping is supported and commonly used for DMVPN hubs.
✗
The hub will use broadcast instead of multicast for all traffic.
Why it's wrong here
The command specifically handles multicast, not broadcast.
Common exam traps
Common exam trap: OSPF can fail even when IP connectivity looks correct
OSPF neighbour formation depends on matching areas, timers, network type, authentication and passive-interface behaviour. Do not choose an answer only because the devices can ping.
Trap categories for this question
Command / output trap
The command specifically handles multicast, not broadcast.
Detailed technical explanation
How to think about this question
OSPF questions usually test the details that control adjacency and route selection. Read the neighbour state, area, router ID and interface configuration before deciding what is wrong.
KKey Concepts to Remember
OSPF neighbours must agree on key parameters.
Router ID selection can affect neighbour relationships and LSDB output.
OSPF cost influences the preferred path.
A route can appear in OSPF information but not become the installed route.
TExam Day Tips
→Check area mismatch first when OSPF adjacency fails.
→Review passive interfaces when a network is advertised but no neighbour forms.
→Use show ip ospf neighbor and show ip route clues carefully.
Key takeaway
OSPF neighbour adjacency depends on matching area, hello/dead timers, network type, and authentication — IP reachability alone is not enough.
Real-world example
How this comes up in practice
A network engineer at a university connects two campus buildings via a fibre link. Both routers run OSPF, but no adjacency forms — even though both routers can ping each other. The engineer finds one router is in area 0 and the other in area 1. OSPF adjacency requires matching area numbers, hello/dead timers, and network type. IP reachability alone is not enough.
Related glossary terms
Concepts from this question explained
These glossary pages explain the core terms tested in this 300-410 question in full detail.
Review OSPF neighbour requirements — matching area type, hello and dead timers, network type, stub flags, and authentication. Study show ip ospf neighbor states (INIT, 2-WAY, FULL). Then practise related 300-410 OSPF questions on adjacency and route selection.
DMVPN — This question tests DMVPN — OSPF neighbours must agree on key parameters..
What is the correct answer to this question?
The correct answer is: The hub will dynamically register spoke NHRP addresses and forward multicast traffic to all registered spokes. — The command 'ip nhrp map multicast dynamic' allows the hub to dynamically learn spoke NHRP addresses for multicast replication, which is essential for routing protocols (e.g., EIGRP, OSPF) that use multicast.
What should I do if I get this 300-410 question wrong?
Review OSPF neighbour requirements — matching area type, hello and dead timers, network type, stub flags, and authentication. Study show ip ospf neighbor states (INIT, 2-WAY, FULL). Then practise related 300-410 OSPF questions on adjacency and route selection.
What is the key concept behind this question?
OSPF neighbours must agree on key parameters.
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