350-501 Architecture Practice Question
In a carrier's network, MPLS-TE tunnels are used to steer traffic away from congested links. The operator configures a tunnel with a bandwidth of 200 Mbps and a dynamic path. The CSPF computation shows a path with sufficient bandwidth, but the tunnel fails to come up. The RSVP neighbor is established. What is the most likely cause?
⚠ Common exam trap
Cisco often tests the distinction between CSPF path computation (which only checks link metrics and TE attributes) and RSVP resource reservation (which performs actual bandwidth admission control), leading candidates to incorrectly assume that a successful CSPF computation guarantees the tunnel will come up.
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
✓
The path message is rejected due to resource reservation failure
The tunnel fails to come up because the CSPF-computed path cannot reserve the requested 200 Mbps bandwidth. Even though the path has sufficient bandwidth on paper, the RSVP resource reservation process may fail due to a lack of available bandwidth at the exact time of reservation, or due to a mismatch in bandwidth pool configuration (e.g., global vs. subpool). Since the RSVP neighbor is established, the issue is specifically with the reservation step, not with reachability or LDP.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
The tunnel destination is not reachable via IGP
Why it's wrong here
If unreachable, CSPF would not find a path.
- ✓
The path message is rejected due to resource reservation failure
Why this is correct
RSVP-TE reserves bandwidth; if not available, tunnel fails.
- ✗
The tunnel interface is down
Why it's wrong here
Tunnel interface is a logical interface; it should be up/up if configured correctly.
- ✗
MPLS LDP is not configured
Why it's wrong here
LDP is not required for RSVP-TE tunnels.
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Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
This 350-501 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 350-501 exam.