hardMultiple Select
CCNP Practice Question: Which three statements about OSPF area types are…
Which three statements about OSPF area types are correct? (Choose three.)
⚠ Common exam trap
Many candidates confuse the LSA types blocked by stub, totally stubby, NSSA, and totally NSSA areas—especially the role of Type 7 LSAs in NSSAs and the fact that totally stubby areas block Type 3 LSAs while stub areas do not.
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
✓
A stub area blocks Type 5 AS External LSAs but allows Type 3 Summary LSAs and a default route.
Option A is correct because a stub area, configured with the area stub command, blocks Type 5 AS External LSAs at the ABR while still permitting Type 3 Summary LSAs, and the ABR injects a default route (Type 3 LSA 0.0.0.0) so internal routers can reach external destinations. Option B is correct because a totally stubby area (area stub no-summary) blocks both Type 5 AS External LSAs and Type 3 Summary LSAs, leaving only a single default route injected by the ABR plus intra-area Type 1 and 2 LSAs. Option D is correct because a standard OSPF area carries Type 1 Router LSAs, Type 2 Network LSAs, Type 3 Summary LSAs, Type 4 ASBR Summary LSAs, and Type 5 AS External LSAs. Option C is incorrect because an NSSA does not import Type 5 LSAs; it uses Type 7 LSAs for external routes originated inside the area, which the ABR translates to Type 5 when flooding into the backbone. Option E is incorrect because a totally NSSA blocks Type 3 Summary LSAs (except the default route) and does not allow Type 5 LSAs; external routes inside it are carried as Type 7 LSAs.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✓
A stub area blocks Type 5 AS External LSAs but allows Type 3 Summary LSAs and a default route.
Why this is correct
Stub areas block Type 5 AS External LSAs at the ABR, preventing external flooding, while Type 3 Summary LSAs still enter and the ABR injects a default route. This matches the stated stub behaviour exactly.
- ✓
A totally stubby area blocks both Type 5 and Type 3 LSAs, injecting only a default route into the area.
Why this is correct
Totally stubby areas extend stub filtering by also blocking Type 3 Summary LSAs, leaving only a default route injected by the ABR. Intra-area Type 1 and 2 LSAs remain, satisfying the stated constraint of blocking both Type 5 and Type 3.
- ✗
A not-so-stubby-area (NSSA) allows Type 5 LSAs to be imported from external networks.
Why it's wrong here
NSSA permits external routes as Type 7 LSAs generated internally, not Type 5 LSAs, which are blocked at the area boundary. It is tempting because NSSA does carry external reachability, but Type 5 flooding is precisely what the NSSA design suppresses.
- ✓
A standard area can contain Type 1, 2, 3, 4, and 5 LSAs.
Why this is correct
Standard OSPF areas carry the full LSA set: Type 1 router, Type 2 network, Type 3 summary, Type 4 ASBR-summary, and Type 5 external LSAs. No filtering is applied, satisfying the stated composition of a standard area.
- ✗
A totally NSSA blocks Type 3 LSAs but allows Type 5 LSAs from external sources.
Why it's wrong here
A totally NSSA blocks Type 3, 4 and 5 LSAs, importing external routes only as Type 7 within the area. It is tempting because NSSA does allow external redistribution, but that occurs via Type 7 LSAs, which the ABR translates to Type 5 at the backbone boundary.
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
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