Quick Answer
The answer is broadcast. On a tunnel interface configured with tunnel mode gre multipoint, the default OSPF network type is broadcast, which means the interface participates in Designated Router and Backup Designated Router elections just like an Ethernet segment. This default occurs because the multipoint GRE (mGRE) interface is designed to emulate a multi-access broadcast medium, allowing dynamic neighbor discovery over the hub-and-spoke topology. On the Cisco CCNP ENARSI 300-410 exam, this concept frequently appears in questions about DMVPN phase 2 or 3 configurations, where a common trap is assuming the network type is point-to-multipoint or non-broadcast. Remember that while mGRE tunnels can support multiple destinations, OSPF treats them as broadcast by default, requiring careful tuning of DR/BDR priorities on the hub to avoid suboptimal routing. A quick memory tip: think of mGRE as a "mini broadcast domain" — the 'B' in broadcast stands for both the default behavior and the need for a BDR election.
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.
What is the default OSPF network type for a tunnel interface configured with 'tunnel mode gre multipoint'?
Broadcast
The default OSPF network type for multipoint GRE tunnels is broadcast.
Point-to-multipoint
Why wrong: This is not the default; it must be configured manually.
Point-to-point
Why wrong: Point-to-point is used for non-multipoint tunnels.
Non-broadcast
Why wrong: Non-broadcast is not the default for multipoint GRE.
Answer choices
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
Broadcast
By default, a multipoint GRE tunnel interface uses the broadcast network type, which requires DR/BDR elections.
Key principle: OSPF neighbour adjacency depends on matching area, hello/dead timers, network type, and authentication — IP reachability alone is not enough.
Answer analysis
For each option: why learners choose it and why it is or isn't the right answer here.
Broadcast
Point-to-multipoint
Why it's wrong here
This is not the default; it must be configured manually.
Point-to-point
Why it's wrong here
Point-to-point is used for non-multipoint tunnels.
Non-broadcast
Why it's wrong here
Non-broadcast is not the default for multipoint GRE.
Common exam traps
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.
Detailed technical explanation
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.
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
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.
What to study next
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.
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FAQ
DMVPN — This question tests DMVPN — OSPF neighbours must agree on key parameters..
The correct answer is: Broadcast — By default, a multipoint GRE tunnel interface uses the broadcast network type, which requires DR/BDR elections.
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.
OSPF neighbours must agree on key parameters.
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Last reviewed: Jun 18, 2026
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