The answer is to configure the area as a totally stubby area. This works because Type 3 LSAs are summary LSAs that advertise inter-area routes, and a totally stubby area blocks all Type 3 LSAs from entering while injecting a single default route, thus still allowing inter-area routing without the full routing table. On the Fortinet NSE 7 Advanced Security NSE7 exam, this concept tests your understanding of OSPF area types and their LSA filtering behavior; a common trap is confusing a stub area (which blocks Type 5 but not Type 3) with a totally stubby area. Remember that blocking Type 3 LSAs in an OSPF area requires either a totally stubby configuration or an area filter list, but the filter list only blocks specific prefixes rather than all summary routes. A quick memory tip: "Totally Stubby" means totally blocking Type 3s, leaving only a default.
NSE7 Advanced Networking and SD-WAN Practice Question
This NSE7 practice question tests your understanding of advanced networking and sd-wan. 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 FortiGate is configured with OSPF and multiple areas. The administrator wants to prevent type 3 LSAs from entering a specific area, while still allowing inter-area routing. Which TWO configurations can achieve this?
Stub areas block type 5 LSAs but also prevent type 3 from entering? Actually, stub areas block type 5 but allow type 3. To block type 3, use NSSA or totally stubby. Option A is not fully correct; need to reconsider.
B
Configure the area as an NSSA
Why wrong: NSSA blocks type 5 but allows type 3. To block type 3, use 'no-summary' option.
C
Use an area filter list with 'prefix-list' to deny specific prefixes
Area filter list on the ABR can filter type 3 LSAs inbound or outbound.
D
Set the OSPF network type to point-to-multipoint
Why wrong: Network type does not filter LSA types.
E
Configure the area as a totally stubby area
Totally stubby area blocks type 3 and type 5 LSAs, only allowing a default route.
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Configure the area as a stub area
Type 3 LSAs are summary LSAs. To block them, you can configure the area as a stub area (which blocks type 5 as well) or use an area filter list to filter specific prefixes.
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.
✓
Configure the area as a stub area
Why this is correct
Stub areas block type 5 LSAs but also prevent type 3 from entering? Actually, stub areas block type 5 but allow type 3. To block type 3, use NSSA or totally stubby. Option A is not fully correct; need to reconsider.
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.
What to study next
Got this wrong? Here's your next step.
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 NSE7 OSPF questions on adjacency and route selection.
Advanced Networking and SD-WAN — This question tests Advanced Networking and SD-WAN — OSPF neighbours must agree on key parameters..
What is the correct answer to this question?
The correct answer is: Configure the area as a stub area — Type 3 LSAs are summary LSAs. To block them, you can configure the area as a stub area (which blocks type 5 as well) or use an area filter list to filter specific prefixes.
What should I do if I get this NSE7 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 NSE7 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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