This 350-501 practice question tests your understanding of networking. The scenario asks you to isolate a root cause — eliminate options that address a different problem before choosing. 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.
An ISP is designing a new core network using MPLS-TE. They require very fast failure detection for link and node failures to minimize traffic loss. Which two technologies should they combine? (Choose two.)
Clue words in this question
Noticing these words before you look at the options changes how you read each choice.
Clue: "minimum / minimize"
Why it matters: Asks for the least resource use — fewest addresses, smallest subnet, lowest overhead. Eliminate over-provisioned options even if they would technically work.
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
MPLS-TE Fast Reroute (FRR)
Option A and D are correct. BFD provides fast failure detection (sub-second), and MPLS-TE Fast Reroute (FRR) provides local protection with backup tunnels. Option B (LDP) does not provide fast detection; Option C (OSPF) alone is too slow; Option E (LSP ping) is for troubleshooting.
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.
✗
OSPF with hello timers set to 1 second
Why it's wrong here
Even with fast hello, OSPF convergence is slower than BFD+FRR.
✓
MPLS-TE Fast Reroute (FRR)
Why this is correct
Provides local repair via backup tunnels.
Clue confirmation
The clue word "minimum / minimize" in the question point toward this answer.
Used for fault detection and isolation, not for fast protection.
✗
Label Distribution Protocol (LDP)
Why it's wrong here
LDP does not provide fast failure detection.
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.
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 350-501 OSPF questions on adjacency and route selection.
Networking — This question tests Networking — OSPF neighbours must agree on key parameters..
What is the correct answer to this question?
The correct answer is: MPLS-TE Fast Reroute (FRR) — Option A and D are correct. BFD provides fast failure detection (sub-second), and MPLS-TE Fast Reroute (FRR) provides local protection with backup tunnels. Option B (LDP) does not provide fast detection; Option C (OSPF) alone is too slow; Option E (LSP ping) is for troubleshooting.
What should I do if I get this 350-501 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 350-501 OSPF questions on adjacency and route selection.
Are there clue words in this question I should notice?
Yes — watch for: "minimum / minimize". Asks for the least resource use — fewest addresses, smallest subnet, lowest overhead. Eliminate over-provisioned options even if they would technically work.
What is the key concept behind this question?
OSPF neighbours must agree on key parameters.
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