300-410 Layer 3 Technologies Practice Question
A network engineer is configuring OSPFv3 on a Cisco IOS XE router. The router has two interfaces: GigabitEthernet0/0 in Area 0 and GigabitEthernet0/1 in Area 1. The engineer wants to ensure that the router acts as an ABR and that inter-area routes are summarized. Which command must be configured under the OSPFv3 router configuration mode to enable ABR functionality?
⚠ Common exam trap
The trap here is assuming that a specific command enables ABR functionality, when in fact ABR status is automatic based on interface area assignments.
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
✓
No additional command is required; ABR is automatic.
ABR status in OSPFv3 is not enabled by a command; it is a role that a router assumes when it has interfaces in multiple areas. The engineer must ensure that the interfaces are assigned to different areas, which is already the case. Commands like area range are used for summarization but do not enable ABR. The router ID is necessary for OSPFv3 operation but not for ABR functionality. Therefore, no additional command is required to make the router an ABR.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✓
No additional command is required; ABR is automatic.
Why this is correct
A router becomes an ABR automatically when it has at least two interfaces in different OSPF areas. No specific command enables ABR functionality. The engineer only needs to ensure that the interfaces are correctly assigned to different areas, which is already stated. Thus, no additional command under router configuration mode is needed to make the router an ABR.
- ✗
area 1 range 2001:db8:1::/64
Why it's wrong here
The area range command is used for inter-area route summarization, but it does not enable ABR functionality. ABR status is automatic when a router has interfaces in multiple areas. This command would be used after ABR status is established to summarize routes, but it is not the command that enables the router to become an ABR.
- ✗
router-id 1.1.1.1
Why it's wrong here
Setting the router ID is necessary for OSPFv3 to operate, but it does not enable ABR functionality. ABR status is determined by having interfaces in multiple areas. Without a router ID, OSPFv3 will not form adjacencies, but this command alone does not make the router an ABR. The scenario already implies interfaces are in different areas, so the router ID is not the key factor.
- ✗
interface GigabitEthernet0/1
Why it's wrong here
Entering interface configuration mode is not done under router configuration mode. The question asks for a command under OSPFv3 router configuration mode. This option is a distractor that might confuse someone who thinks they need to configure the interface, but ABR functionality is not enabled by entering interface mode; it is inherent when the router has interfaces in multiple areas.
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.