Question 1hardmultiple choice
Full question →hardmultiple choiceObjective-mapped
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
Good practice is not just finding the correct option. The wrong answers often show the exact trap the exam wants you to fall into.
A
Best answer
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
Distractor review
Totally stubby area
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
Distractor review
Not-so-stubby-area (NSSA)
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
Distractor review
Normal area
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 trap
Common exam trap: OSPF can fail even when IP connectivity looks correct
OSPF neighbour formation depends on matching areas, timers, network type, authentication and passive-interface behaviour. Do not choose an answer only because the devices can ping.
Technical deep dive
How to think about this question
OSPF questions usually test the details that control adjacency and route selection. Read the neighbour state, area, router ID and interface configuration before deciding what is wrong.
KKey Concepts to Remember
- OSPF neighbours must agree on key parameters.
- Router ID selection can affect neighbour relationships and LSDB output.
- OSPF cost influences the preferred path.
- A route can appear in OSPF information but not become the installed route.
TExam Day Tips
- Check area mismatch first when OSPF adjacency fails.
- Review passive interfaces when a network is advertised but no neighbour forms.
- Use show ip ospf neighbor and show ip route clues carefully.
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More questions from this exam
Keep practising from the same exam bank, or move into a focused topic page if this question exposed a weak area.
Question 1
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Question 2
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Question 3
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Question 4
A network administrator is connecting two switches to increase bandwidth and provide redundancy. Which technology should be used to combine multiple physical links into a single logical link?
Question 5
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Question 6
A network administrator is troubleshooting a connectivity issue and suspects the problem is related to the physical cabling. At which layer of the OSI model should the administrator begin their investigation?
FAQ
Questions learners often ask
What does this N10-009 question test?
OSPF neighbours must agree on key parameters.
What is the correct answer to this question?
The correct answer is: Stub area — A totally stubby area blocks Type 3 LSAs (inter-area summary routes) and Type 5 LSAs (external routes), and uses a default route only. A stub area blocks Type 5 LSAs but allows Type 3 LSAs. A not-so-stubby-area (NSSA) allows Type 7 LSAs for external routes and can also block Type 5 LSAs. The question says the router must learn inter-area routes (Type 3 LSAs) but not Type 5 LSAs; this matches the stub area definition. A totally stubby area would block Type 3 LSAs as well, which is not what is required.
What should I do if I get this N10-009 question wrong?
Then try more questions from the same exam bank and focus on understanding why the wrong options are tempting.
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