350-401 Infrastructure Practice Question
A network administrator is configuring a new Cisco IOS router and needs to enable OSPFv3 for IPv6 on an interface. The interface is already configured with an IPv6 address. Which command must be entered in interface configuration mode to enable OSPFv3 on that interface?
⚠ Common exam trap
Watch out — candidates often confuse OSPFv2 for IPv4 with OSPFv3 for IPv6, leading to the use of 'ip ospf' instead of 'ipv6 ospf'.
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
✓
ipv6 ospf 1 area 0
To enable OSPFv3 for IPv6 on an interface in Cisco IOS, the correct interface configuration command is 'ipv6 ospf <process-id> area <area-id>'. This command activates OSPFv3 on the interface and links it to the specified OSPFv3 process and area. The process ID must match the one defined in the global 'ipv6 router ospf' command. Without this command, the interface will not participate in OSPFv3 routing.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✓
ipv6 ospf 1 area 0
Why this is correct
This command enables OSPFv3 on the interface and associates it with OSPF process 1 and area 0. It is the correct way to enable OSPFv3 for IPv6 on an interface in Cisco IOS. The process ID must match the one configured in the global 'ipv6 router ospf' command. This command is essential for OSPFv3 operation on a per-interface basis.
- ✗
ospfv3 1 ipv6 area 0
Why it's wrong here
This command is used to enable OSPFv3 for IPv6 on an interface in some Cisco platforms, but it is not the standard IOS command. The correct command in Cisco IOS for OSPFv3 on an interface is 'ipv6 ospf <process-id> area <area-id>'. The 'ospfv3' command is typically used in Cisco IOS XR or other operating systems. Therefore, this option is incorrect for standard Cisco IOS.
- ✗
ipv6 router ospf 1
Why it's wrong here
This command is used in global configuration mode to enable the OSPFv3 routing process and enter router configuration mode. It does not enable OSPFv3 on an interface. To enable OSPFv3 on an interface, the 'ipv6 ospf' command must be used in interface configuration mode. This option is a global command, not an interface command.
- ✗
ip ospf 1 area 0
Why it's wrong here
This command enables OSPFv2 for IPv4 on the interface. It does not enable OSPFv3 for IPv6. The 'ip ospf' command is used for IPv4 OSPFv2, while 'ipv6 ospf' is used for IPv6 OSPFv3. Using this command would not enable IPv6 routing via OSPFv3 and would not meet the requirement.
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 350-401 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 350-401 exam.