- A
Stub area
A stub area blocks Type 5 LSAs (external routes) but allows Type 3 LSAs (inter-area routes). It also uses a default route for external destinations.
- B
Totally stubby area
Why wrong: A totally stubby area blocks both Type 5 and Type 3 LSAs, replacing them with a default route. This would prevent learning inter-area routes, which the administrator wants.
- C
Not-so-stubby-area (NSSA)
Why wrong: NSSA blocks Type 5 LSAs but allows Type 7 LSAs for external routes redistributed from within the area. It still allows Type 3 LSAs. However, the question does not mention redistributing external routes into area 1; a stub area is simpler.
- D
Normal area
Why wrong: A normal area does not block any LSA types; it would receive both Type 3 and Type 5 LSAs, which does not meet the requirement to reduce routing table size by blocking Type 5 LSAs.
Quick Answer
The answer is a stub area. This OSPF area type is the correct choice because it blocks Type 5 LSAs (external routes injected by an ASBR) from entering the area while still permitting Type 3 LSAs (inter-area routes), exactly matching the requirement to prevent external routes from area 0 while maintaining connectivity to other areas and reducing the routing table size. On the CompTIA Network+ N10-009 exam, this tests your understanding of OSPF area types and LSA filtering—a common trap is confusing a stub area with a totally stubby area, which also blocks Type 3 LSAs, or with a not-so-stubby area (NSSA), which allows some external routes. Remember the key distinction: a stub area says "no to Type 5s, yes to Type 3s." A helpful memory tip is to think of a "stub" as a short, blocked pipe—it stops external (Type 5) water from flowing in, but still lets inter-area (Type 3) water pass through.
N10-009 Network Implementation Practice Question
This N10-009 practice question tests your understanding of network implementation. This is a configuration task: choose the command set that satisfies every stated requirement. Small differences — like 'secret' vs 'password' or 'transport input ssh' vs 'all' — change whether the answer is correct. After answering, compare your reasoning against the explanation and wrong-answer breakdown below. Once you have made your selection, read the full explanation to reinforce the concept and understand why each distractor is designed to mislead on exam day.
A network administrator is configuring OSPF on routers in a multi-area network. The administrator wants to ensure that a router in area 1 does not learn external routes (Type 5 LSAs) injected by an ASBR in area 0, but it must still learn inter-area routes (Type 3 LSAs). The administrator wants to reduce the routing table size. Which OSPF area type should be configured for area 1?
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
Stub area
A stub area blocks Type 5 LSAs (external routes) from entering the area while still allowing Type 3 LSAs (inter-area routes). This meets the requirement of preventing external routes from the ASBR in area 0 from being learned by routers in area 1, while still permitting inter-area routing and reducing the routing table size.
Key principle: Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✓
Stub area
Why this is correct
A stub area blocks Type 5 LSAs (external routes) but allows Type 3 LSAs (inter-area routes). It also uses a default route for external destinations.
Related concept
Read the scenario before looking for a memorised answer.
- ✗
Totally stubby area
Why it's wrong here
A totally stubby area blocks both Type 5 and Type 3 LSAs, replacing them with a default route. This would prevent learning inter-area routes, which the administrator wants.
- ✗
Not-so-stubby-area (NSSA)
Why it's wrong here
NSSA blocks Type 5 LSAs but allows Type 7 LSAs for external routes redistributed from within the area. It still allows Type 3 LSAs. However, the question does not mention redistributing external routes into area 1; a stub area is simpler.
- ✗
Normal area
Why it's wrong here
A normal area does not block any LSA types; it would receive both Type 3 and Type 5 LSAs, which does not meet the requirement to reduce routing table size by blocking Type 5 LSAs.
Common exam traps
Common exam trap: answer the scenario, not the keyword
Cisco often tests the distinction between stub and totally stubby areas, where candidates mistakenly choose totally stubby when they only need to block external routes but still require inter-area routes.
Detailed technical explanation
How to think about this question
OSPF stub areas use a default route (0.0.0.0/0) injected by the ABR to reach external destinations, eliminating the need for Type 5 LSAs. The ABR in a stub area does not flood Type 5 LSAs, but it still forwards Type 3 summaries, ensuring inter-area connectivity. This design is defined in RFC 2328 and is commonly used to simplify routing tables in non-backbone areas that do not need external route visibility.
KKey Concepts to Remember
- Read the scenario before looking for a memorised answer.
- Find the constraint that changes the correct option.
- Eliminate answers that are true in general but not in this case.
TExam Day Tips
- Watch for words such as best, first, most likely and least administrative effort.
- Review why wrong options are wrong, not only why the correct option is correct.
Key takeaway
Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Real-world example
How this comes up in practice
A network engineer at a university connects two campus buildings via a fibre link. Both routers run OSPF, but no adjacency forms — even though both routers can ping each other. The engineer finds one router is in area 0 and the other in area 1. OSPF adjacency requires matching area numbers, hello/dead timers, and network type. IP reachability alone is not enough.
What to study next
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FAQ
Questions learners often ask
What does this N10-009 question test?
Network Implementation — This question tests Network Implementation — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: Stub area — A stub area blocks Type 5 LSAs (external routes) from entering the area while still allowing Type 3 LSAs (inter-area routes). This meets the requirement of preventing external routes from the ASBR in area 0 from being learned by routers in area 1, while still permitting inter-area routing and reducing the routing table size.
What should I do if I get this N10-009 question wrong?
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
What is the key concept behind this question?
Read the scenario before looking for a memorised answer.
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Last reviewed: Jun 11, 2026
This N10-009 practice question is part of Courseiva's free CompTIA 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 N10-009 exam.
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