350-401 Infrastructure Practice Question
A network engineer is configuring a Cisco IOS router to support OSPFv3 for IPv6. The router is connected to two OSPFv3 areas: area 0 and area 1. The engineer wants to summarize the IPv6 routes from area 1 into area 0 using the prefix 2001:DB8:1::/48. Which command should be used on the area border router (ABR)?
⚠ Common exam trap
Many candidates confuse inter-area summarization with external summarization, or using the wrong area ID in the command.
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
✓
area 1 range 2001:DB8:1::/48
In OSPFv3, inter-area route summarization is configured on an ABR using the 'area <area-id> range <prefix>' command. The area ID specifies the source area whose routes are to be summarized. Here, routes from area 1 are summarized into area 0 using the prefix 2001:DB8:1::/48. The other commands either do not exist, are for external summarization, or specify the wrong area.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✓
area 1 range 2001:DB8:1::/48
Why this is correct
This command configures inter-area route summarization for OSPFv3 on the ABR. The 'area 1 range' command tells the ABR to advertise a single summary route for the specified prefix into other areas. It must be configured under IPv6 router OSPF configuration mode. This is the correct way to summarize OSPFv3 routes between areas.
- ✗
summary-address 2001:DB8:1::/48
Why it's wrong here
The 'summary-address' command is used for summarizing external routes redistributed into OSPFv3, not inter-area routes. It is configured under router ospfv3 configuration mode. For inter-area summarization, the 'area range' command is required. Using 'summary-address' would not summarize routes from area 1 into area 0.
- ✗
ipv6 ospf summary-prefix 2001:DB8:1::/48
Why it's wrong here
The command 'ipv6 ospf summary-prefix' does not exist in Cisco IOS. OSPFv3 summarization is configured using the 'area range' command under router ospfv3 configuration mode. This option is a distractor that might be confused with other summarization commands like 'summary-address' for external routes.
- ✗
area 0 range 2001:DB8:1::/48
Why it's wrong here
This command would attempt to summarize routes within area 0, but the requirement is to summarize routes from area 1 into area 0. The area ID in the command must match the area from which the routes are being summarized. Area 0 is the backbone area, and summarizing there would affect different routes. The correct area is 1.
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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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
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