The answer is Type 3 (Summary LSA). This is correct because an Area Border Router (ABR) uses Type 3 LSAs to advertise inter-area routes, including a default route, into regular areas by setting the destination network to 0.0.0.0. In OSPF, Type 3 LSAs are the only mechanism an ABR has to summarize or inject a default route across area boundaries, as they describe networks from one area to another without carrying topology details. On the Cisco CCNP ENARSI 300-410 exam, this concept tests your understanding of how ABRs generate and flood summary LSAs, often appearing in questions about default route propagation or area filtering. A common trap is confusing Type 3 with Type 5 (external) or Type 4 (ASBR summary) LSAs—remember that only a Type 3 LSA carries a default route from an ABR into a regular area. For a memory tip, think “3 for the ABR’s summary spree, default route to 0.0.0.0 is key.”
300-410 Device Management Practice Question
This 300-410 practice question tests your understanding of device management. Read the scenario carefully and evaluate each option against the stated constraints before committing to an answer. 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.
Which OSPF LSA type is used to describe a default route injected into a regular area by an Area Border Router (ABR)?
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Type 3 (Summary LSA)
Type 3 LSAs are summary LSAs generated by ABRs to advertise networks from one area to another. When an ABR injects a default route into a regular area, it uses a Type 3 LSA with a destination of 0.0.0.0.
Key principle: OSPF neighbour adjacency depends on matching area, hello/dead timers, network type, and authentication — IP reachability alone is not enough.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
✗
Type 1 (Router LSA)
Why it's wrong here
Type 1 LSAs describe a router's own interfaces and links within an area.
✗
Type 2 (Network LSA)
Why it's wrong here
Type 2 LSAs are generated by the Designated Router for multi-access networks.
✓
Type 3 (Summary LSA)
Why this is correct
Correct: ABRs use Type 3 LSAs to advertise inter-area routes, including default routes.
Type 5 LSAs are used for external routes redistributed into OSPF, not for inter-area default routes.
Common exam traps
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.
Detailed technical explanation
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.
Key takeaway
OSPF neighbour adjacency depends on matching area, hello/dead timers, network type, and authentication — IP reachability alone is not enough.
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.
Related glossary terms
Concepts from this question explained
These glossary pages explain the core terms tested in this 300-410 question in full detail.
Review OSPF neighbour requirements — matching area type, hello and dead timers, network type, stub flags, and authentication. Study show ip ospf neighbor states (INIT, 2-WAY, FULL). Then practise related 300-410 OSPF questions on adjacency and route selection.
Device Management — This question tests Device Management — OSPF neighbours must agree on key parameters..
What is the correct answer to this question?
The correct answer is: Type 3 (Summary LSA) — Type 3 LSAs are summary LSAs generated by ABRs to advertise networks from one area to another. When an ABR injects a default route into a regular area, it uses a Type 3 LSA with a destination of 0.0.0.0.
What should I do if I get this 300-410 question wrong?
Review OSPF neighbour requirements — matching area type, hello and dead timers, network type, stub flags, and authentication. Study show ip ospf neighbor states (INIT, 2-WAY, FULL). Then practise related 300-410 OSPF questions on adjacency and route selection.
What is the key concept behind this question?
OSPF neighbours must agree on key parameters.
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