easyMultiple ChoiceObjective-mapped
300-410 Practice Question: Is troubleshooting an IPv6 routing issue where a…
A network engineer is troubleshooting an IPv6 routing issue where a router is not learning routes from an OSPFv3 neighbor. The engineer checks the interface and finds an inbound IPv6 ACL that permits only OSPFv3 packets with a specific area ID in the packet. The ACL is using the 'ospfv3' keyword to match packets. The engineer also notices that the OSPFv3 neighbor is in a different area. What is the most likely cause of the route learning failure?
⚠ Common exam trap
Cisco often tests the nuance that the 'ospfv3' ACL keyword can match not only the protocol but also the area ID field, and candidates mistakenly assume the ACL only matches the protocol type (OSPFv3) without considering the area ID filter.
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 ACL is dropping OSPFv3 packets from the neighbor because they contain a different area ID than what the ACL permits.
The ACL uses the 'ospfv3' keyword to match OSPFv3 packets and permits only those with a specific area ID. Since the neighbor is in a different area, its OSPFv3 packets contain a different area ID in the OSPFv3 header, causing the ACL to deny them. This prevents the router from receiving Hello packets and establishing adjacency, so routes are not learned.
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 ACL is dropping OSPFv3 packets from the neighbor because they contain a different area ID than what the ACL permits.
Why this is correct
Correct because the ACL permits only packets with a specific area ID, and the neighbor is in a different area, so its packets are dropped.
- ✗
The OSPFv3 process is not configured with the correct router ID.
Why it's wrong here
Incorrect because the neighbor relationship is not forming due to the ACL, not the router ID.
- ✗
The interface is not enabled for OSPFv3.
Why it's wrong here
Incorrect because the neighbor is sending packets, indicating OSPFv3 is enabled on the interface.
- ✗
The ACL is applied outbound, blocking the OSPFv3 packets from being sent.
Why it's wrong here
Incorrect because the ACL is inbound, as stated.
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
Learn chapter
Introduction to ENARSI Exam and Network Fundamentals
Key term
IPv6 Next Hop Resolution
IPv6 Next Hop Resolution is the process a router uses to determine the next router or destination device to which a packet should be forwarded, based on the destination IPv6 address and the routing table.
Key term
IPv6 Routing OSPFv3
OSPFv3 is a routing protocol that lets routers share information about how to reach destinations in an IPv6 network, updating routes automatically as the network changes.
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Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
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.