hardMultiple Choice
300-410 Practice Question: An engineer configures OSPFv3 with a filter-list…
An engineer configures OSPFv3 with a filter-list on an ABR to filter prefixes. After configuration, the routes are still being advertised. Which is the most likely explanation?
⚠ Common exam trap
300-410 often tests the LSA-type scope of OSPF filter-lists—candidates assume filter-list filters all routes, but it only affects inter-area (Type 3) LSAs, not external routes.
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 filter-list only filters inter-area prefixes, not external routes.
OSPFv3 filter-lists applied with the 'area filter-list' command only filter inter-area (Type 3) LSAs, not external (Type 5/7) routes. If the engineer is trying to filter external prefixes redistributed into OSPFv3, the filter-list will have no effect, which explains why routes are still advertised.
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 filter-list only filters inter-area prefixes, not external routes.
Why this is correct
OSPFv3 filter-lists applied to an ABR restrict prefixes exchanged between areas, so they only affect inter-area (type 3) LSAs. External prefixes redistributed into OSPFv3 are carried in type 5 or 7 LSAs, which the filter-list does not examine, leaving them advertised unchanged.
- ✗
The filter-list is applied to the wrong area.
Why it's wrong here
An OSPFv3 filter-list on an ABR filters prefixes within a specified area, so applying it to the wrong area leaves the intended routes advertised. It tempts because area mismatch is a common configuration error, but the filter-list direction and prefix-list contents also govern whether filtering takes effect.
- ✗
The filter-list uses an incorrect prefix-list.
Why it's wrong here
An incorrect prefix-list would simply match nothing, so the filter-list would still suppress the intended prefixes; the symptom of routes remaining advertised points elsewhere. Prefix-lists are the correct tool for OSPFv3 filter-lists, so this would be the right choice when the list itself is genuinely mis-typed.
- ✗
The OSPFv3 process needs to be restarted.
Why it's wrong here
OSPFv3 applies filter-lists dynamically to the link-state database as they are configured, so no process restart is required and restarting would not change the outcome. Restarting the process is the right step when a stuck adjacency or stale configuration needs clearing, not for prefix filtering.
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
About these practice questions
One of 1,401 original 300-410 practice questions on Courseiva, each with a full explanation and wrong-answer analysis — not exam dumps or protected exam content. Learn why practice questions differ from exam dumps →
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.