300-410 Infrastructure Services Practice Question
A network administrator is troubleshooting an OSPFv3 network. Routers R1 and R2 are directly connected on a point-to-point link. R1 is configured with OSPFv3 area 0, and R2 is configured with OSPFv3 area 1. The administrator notices that no OSPFv3 adjacency forms between them. What is the most likely cause?
⚠ Common exam trap
The trap here is focusing on advanced OSPFv3 features like router ID uniqueness while overlooking the fundamental requirement that area numbers must match on a link.
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 OSPFv3 area numbers do not match on the link.
For OSPFv3 to form an adjacency, both routers on a common link must be configured in the same OSPF area. In this scenario, R1 is in area 0 and R2 is in area 1, which violates this requirement. The hello packets will be ignored, and no adjacency will form. Other potential issues like duplicate router IDs or interface configuration are not indicated by the symptoms.
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 OSPFv3 area numbers do not match on the link.
Why this is correct
OSPFv3, like OSPFv2, requires that routers on the same link be in the same area to form an adjacency. Since R1 is in area 0 and R2 is in area 1, the hello packets will not be accepted, and the adjacency will not form. This is the most likely cause of the problem described.
- ✗
The OSPFv3 router IDs are not unique.
Why it's wrong here
Duplicate router IDs would prevent adjacency formation, but the scenario does not indicate that this is the case. The explicit mismatch of area numbers on a point-to-point link is a more direct cause. OSPFv3 requires that both ends of a link belong to the same area for an adjacency to form, so the area mismatch is the primary issue here.
- ✗
The OSPFv3 process is not enabled on the interfaces.
Why it's wrong here
If OSPFv3 were not enabled on the interfaces, the routers would not send or receive hello packets at all. However, the scenario implies that OSPFv3 is configured and running, but the area mismatch prevents adjacency. While lack of interface configuration is a possible issue, the area mismatch is the specific and likely cause given the details.
- ✗
The OSPFv3 network type is mismatched.
Why it's wrong here
A mismatch in network type (e.g., broadcast vs. point-to-point) can prevent adjacency, but the scenario specifies a point-to-point link and does not indicate a mismatch. The area number mismatch is explicitly stated and is a definite barrier to adjacency formation. Therefore, network type mismatch is not the most likely cause in this case.
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
About these practice questions
This 300-410 question is part of Courseiva's 1,401-question bank — original exam-style content with full explanations and wrong-answer analysis, never real exam questions or exam dumps. Learn why practice questions differ from exam dumps →
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.