- A
MPLS-TE uses RSVP-TE to signal LSPs and reserve resources.
Correct because RSVP-TE is the signaling protocol for MPLS-TE, enabling bandwidth reservation and explicit paths.
- B
OSPF or IS-IS can be extended to carry TE link attributes.
Correct because OSPF TE extensions (opaque LSAs) and IS-IS TE extensions advertise link bandwidth, delay, etc.
- C
MPLS-TE allows traffic to follow paths that differ from the IGP shortest path.
Correct because MPLS-TE can steer traffic onto explicit paths that are not the IGP shortest path.
- D
MPLS-TE relies on LDP to distribute labels for TE tunnels.
Why wrong: Incorrect because MPLS-TE uses RSVP-TE to assign labels; LDP is not used for TE tunnels.
- E
MPLS-TE uses BGP to compute the best path for TE LSPs.
Why wrong: Incorrect because MPLS-TE uses CSPF (Constrained SPF) based on IGP TE database, not BGP.
Quick Answer
The correct answer is that MPLS traffic engineering allows traffic to follow paths that differ from the IGP shortest path. This is true because MPLS-TE uses RSVP-TE signaling to establish explicit label-switched paths, enabling traffic to be routed based on constraints like bandwidth and delay rather than the default IGP metric. The Constrained Shortest Path First (CSPF) algorithm computes these paths using extended link-state advertisements from OSPF or IS-IS, which advertise attributes such as available bandwidth and link delay. On the ENCOR 350-401 exam, this concept tests your understanding of how MPLS-TE decouples traffic from IGP routing, with a common trap being the assumption that LDP handles TE label assignment—it does not, as RSVP-TE manages both signaling and label distribution for TE tunnels. A useful memory tip: think of RSVP-TE as the “reservation” protocol that books bandwidth and labels, while CSPF is the “map” that avoids the IGP’s default path.
350-401 MPLS Practice Question
This 350-401 practice question tests your understanding of mpls. 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 three statements about MPLS traffic engineering (MPLS-TE) are true? (Choose three.)
Answer choices
Why each option matters
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
MPLS-TE uses RSVP-TE to signal LSPs and reserve resources.
MPLS-TE uses RSVP-TE to signal explicit paths and reserve bandwidth. It can use OSPF or IS-IS extended LSAs to advertise link attributes like bandwidth and delay. MPLS-TE allows traffic to be routed away from shortest-path IGP routes. LDP is not involved in TE; RSVP-TE handles label assignment for TE tunnels. MPLS-TE does not use BGP for path computation; it uses CSPF (Constrained Shortest Path First).
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.
- ✓
MPLS-TE uses RSVP-TE to signal LSPs and reserve resources.
Why this is correct
Correct because RSVP-TE is the signaling protocol for MPLS-TE, enabling bandwidth reservation and explicit paths.
Related concept
OSPF neighbours must agree on key parameters.
- ✓
OSPF or IS-IS can be extended to carry TE link attributes.
- ✓
MPLS-TE allows traffic to follow paths that differ from the IGP shortest path.
Why this is correct
Correct because MPLS-TE can steer traffic onto explicit paths that are not the IGP shortest path.
Related concept
OSPF neighbours must agree on key parameters.
- ✗
MPLS-TE relies on LDP to distribute labels for TE tunnels.
Why it's wrong here
Incorrect because MPLS-TE uses RSVP-TE to assign labels; LDP is not used for TE tunnels.
- ✗
MPLS-TE uses BGP to compute the best path for TE LSPs.
Why it's wrong here
Incorrect because MPLS-TE uses CSPF (Constrained SPF) based on IGP TE database, not BGP.
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 350-401 OSPF questions on adjacency and route selection.
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FAQ
Questions learners often ask
What does this 350-401 question test?
MPLS — This question tests MPLS — OSPF neighbours must agree on key parameters..
What is the correct answer to this question?
The correct answer is: MPLS-TE uses RSVP-TE to signal LSPs and reserve resources. — MPLS-TE uses RSVP-TE to signal explicit paths and reserve bandwidth. It can use OSPF or IS-IS extended LSAs to advertise link attributes like bandwidth and delay. MPLS-TE allows traffic to be routed away from shortest-path IGP routes. LDP is not involved in TE; RSVP-TE handles label assignment for TE tunnels. MPLS-TE does not use BGP for path computation; it uses CSPF (Constrained Shortest Path First).
What should I do if I get this 350-401 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 350-401 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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Last reviewed: Jun 18, 2026
This 350-401 practice question is part of Courseiva's free Cisco certification practice question bank. Courseiva provides original exam-style practice questions with explanations, topic-based practice, mock exams, readiness tracking, and study analytics to help learners prepare for the 350-401 exam.
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