300-410 Layer 3 Technologies Practice Question
A network administrator is troubleshooting an OSPFv3 network. Router R1 is configured with the following:
ipv6 unicast-routing
interface GigabitEthernet0/0
ipv6 address 2001:DB8:1::1/64 ipv6 ospf 1 area 0 ipv6 ospf network point-to-point !
router ospf 1
router-id 1.1.1.1 !
R1 is not forming an adjacency with R2, which is configured with:
interface GigabitEthernet0/0
ipv6 address 2001:DB8:1::2/64 ipv6 ospf 1 area 0 ipv6 ospf network broadcast !
router ospf 1
router-id 2.2.2.2
What is the most likely reason for the adjacency failure?
⚠ Common exam trap
The trap here is assuming that OSPFv3 automatically negotiates network type or that link-local addresses must be manually configured, when the real issue is the mismatch in network type.
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 network type mismatch (point-to-point vs. broadcast) prevents the routers from forming an adjacency.
OSPF network types must be consistent on both ends of a link for an adjacency to form. R1 is configured with ipv6 ospf network point-to-point, while R2 uses broadcast. This mismatch leads to differing hello packet handling and prevents the adjacency. To resolve, configure both interfaces with the same network type, either point-to-point or broadcast.
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 router-id must be the same on both routers for an adjacency to form.
Why it's wrong here
OSPF router-ids must be unique within the OSPF domain; they do not need to match. In fact, duplicate router-ids can cause issues. The adjacency failure is due to the network type mismatch, not the router-id configuration.
- ✗
OSPFv3 requires the use of link-local addresses for adjacency formation, and they are not configured.
Why it's wrong here
OSPFv3 does use link-local addresses for neighbor discovery and next-hop calculation, but they are automatically generated when IPv6 is enabled on the interface. They do not need to be manually configured. The absence of explicit link-local addresses is not the cause of the adjacency failure.
- ✗
OSPFv3 requires the router-id to be configured under the interface, not under the router ospf process.
Why it's wrong here
In OSPFv3, the router-id is configured under the router ospf process, similar to OSPFv2. Configuring it under the interface is not required and would not cause an adjacency failure. The issue is the network type mismatch between the two routers.
- ✓
The network type mismatch (point-to-point vs. broadcast) prevents the routers from forming an adjacency.
Why this is correct
OSPF network types must match on both sides of a link for an adjacency to form. R1 is configured as point-to-point, while R2 is broadcast. This mismatch causes hello packets to be interpreted differently, and the adjacency will not form. Both routers must use the same network type, either point-to-point or broadcast.
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.
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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.