mediumMultiple Choice
300-410 Practice Question: Configures a DMVPN spoke with OSPF as the routing…
A network engineer configures a DMVPN spoke with OSPF as the routing protocol:
interface Tunnel0 ip address 10.0.0.2 255.255.255.0 ip nhrp network-id 100 ip nhrp nhs 10.0.0.1
tunnel source GigabitEthernet0/0 tunnel mode gre multipoint
ip nhrp map 10.0.0.1 192.168.1.1 ip nhrp map multicast 192.168.1.1
!
router ospf 1 network 10.0.0.0 0.0.0.255 area 0
!
What is a common issue with OSPF in this DMVPN Phase 2 configuration?
⚠ Common exam trap
300-410 often tests the misconception that OSPF automatically adapts to DMVPN topologies, when in fact the default broadcast network type causes DR/BDR election problems that must be manually corrected.
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
✓
OSPF will elect a DR/BDR on the hub, which can cause suboptimal routing and adjacency issues.
In a DMVPN Phase 2 configuration, the tunnel interface is a multipoint GRE (mGRE) interface, which by default is treated as a broadcast network by OSPF. On a broadcast network, OSPF elects a DR and BDR, and in DMVPN the hub typically becomes the DR while spokes become DROTHERs. This causes spokes to form full adjacencies only with the hub, and inter-spoke traffic must transit the hub, producing suboptimal routing and potential adjacency or next-hop issues.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✓
OSPF will elect a DR/BDR on the hub, which can cause suboptimal routing and adjacency issues.
Why this is correct
On a multipoint tunnel, OSPF treats the interface as broadcast, electing a DR and BDR. The hub usually becomes DR, so all spoke routes funnel through it, producing suboptimal paths and preventing direct spoke-to-spoke adjacencies in Phase 2.
- ✗
OSPF will not form adjacencies because of NHRP authentication.
Why it's wrong here
NHRP authentication is not configured in this spoke, so it cannot block adjacency formation. It is tempting because mismatched NHRP authentication keys do break spoke-to-hub registration, but that is a separate feature from OSPF neighbour establishment.
- ✗
OSPF will use point-to-point network type by default.
Why it's wrong here
GRE multipoint tunnels default to OSPF network type broadcast, not point-to-point, so DR election occurs across the NBMA cloud. It is tempting because point-to-point is the recommended setting for DMVPN Phase 2, but it must be configured explicitly.
- ✗
OSPF will automatically adjust to the DMVPN environment.
Why it's wrong here
OSPF does not detect or adapt to DMVPN automatically; the tunnel interface keeps its broadcast network type and elects a DR unless changed. It is tempting because NHRP resolves next hops dynamically, but OSPF neighbour behaviour still requires manual tuning.
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
Advanced EIGRP Features (Stub, Load Balancing, Named Mode)
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.