The correct answer is that OSPF can support multiple areas with a backbone area 0, and this is enabled by the use of distinct LSA types to advertise different categories of routing information. Specifically, OSPF relies on Type 1 Router LSAs for intra-area links, Type 2 Network LSAs for transit networks, Type 3 Summary LSAs for inter-area routes, and Type 5 AS-External LSAs for routes redistributed from outside the OSPF domain. This LSA-type differentiation is fundamental to OSPF’s link-state architecture, allowing efficient flooding and route computation within and across areas while keeping each area’s topology isolated. On the Cisco SPCOR 350-501 exam, this concept tests your understanding of multi-area design in service provider networks, where backbone area 0 must be contiguous and all other areas connect to it. A common trap is confusing Type 3 and Type 5 LSAs, but remember: Type 3 stays inside the OSPF domain, while Type 5 brings external routes in. A useful memory tip is “1 and 2 stay local, 3 crosses areas, 5 comes from outside.”
350-501 Networking Practice Question
This 350-501 practice question tests your understanding of networking. 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 TWO statements correctly describe the use of OSPF in a service provider network?
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
OSPF uses different LSA types to advertise different types of routing information.
Option B is correct because OSPF uses different LSA types (e.g., Type 1 Router LSA, Type 2 Network LSA, Type 3 Summary LSA, Type 5 AS-External LSA) to advertise different categories of routing information, such as router links, network links, inter-area routes, and external routes. This LSA-type differentiation is fundamental to OSPF's link-state architecture, enabling efficient flooding and route computation within and across areas.
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.
✗
OSPF uses the Bellman-Ford algorithm to compute routes.
Common exam trap: answer the scenario, not the keyword
Cisco often tests the distinction between link-state and distance-vector protocols, and candidates may mistakenly associate OSPF with Bellman-Ford or TLVs due to superficial similarities with other protocols like IS-IS or EIGRP.
Detailed technical explanation
How to think about this question
OSPF's multi-area design with backbone area 0 (Option D) is critical for scalability in service provider networks, as it allows summarization and reduces LSA flooding between areas. The backbone area must be contiguous and all non-backbone areas must connect directly to it, ensuring loop-free inter-area routing via inter-area (Type 3) LSAs. In real-world SP deployments, OSPF is often used for IGP within a single AS, with careful area design to isolate failures and optimize convergence.
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
Got this wrong? Here's your next step.
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
Networking — This question tests Networking — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: OSPF uses different LSA types to advertise different types of routing information. — Option B is correct because OSPF uses different LSA types (e.g., Type 1 Router LSA, Type 2 Network LSA, Type 3 Summary LSA, Type 5 AS-External LSA) to advertise different categories of routing information, such as router links, network links, inter-area routes, and external routes. This LSA-type differentiation is fundamental to OSPF's link-state architecture, enabling efficient flooding and route computation within and across areas.
What should I do if I get this 350-501 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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Question Discussion
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