350-501 Architecture Practice Question
A service provider is implementing MPLS-TE with FRR (Fast Reroute) using one-to-one backup tunnels. After activation, they notice that the number of labels in the forwarding table has increased significantly. What is the most likely reason for this increase?
⚠ Common exam trap
Cisco often tests the distinction between one-to-one and facility backup, where candidates may confuse the label increase with a signaling or PHP issue, rather than recognizing it as a direct consequence of the one-to-one backup design.
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
✓
One-to-one backup creates a unique backup tunnel for each protected LSP
One-to-one backup tunnels in MPLS-TE FRR create a dedicated backup LSP for each protected primary LSP. This means every primary LSP gets its own unique set of labels for the backup path, leading to a significant increase in the number of labels in the forwarding table. In contrast, facility backup shares a single bypass tunnel among multiple protected LSPs, which conserves labels.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✓
One-to-one backup creates a unique backup tunnel for each protected LSP
Why this is correct
Each protected LSP gets its own backup tunnel, increasing label count linearly.
- ✗
RSVP-TE signaling is not properly aggregating labels
Why it's wrong here
RSVP-TE signaling does not cause label increase; it's the backup method.
- ✗
Penultimate Hop Popping (PHP) is disabled
Why it's wrong here
PHP affects label removal, not number of labels in the forwarding table.
- ✗
Facility backup is being used instead of one-to-one
Why it's wrong here
Facility backup shares backup tunnels, reducing label overhead.
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JA
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.