The answer is MPLS TE Fast Reroute (FRR) because it provides sub-50 millisecond local protection by pre-computing backup bypass tunnels that can be manually triggered during planned maintenance on a core LSR, ensuring zero packet loss. This feature works by establishing a pre-signaled backup path around the protected link or node; when an operator administratively shuts down the interface for maintenance, the head-end LSR instantly switches traffic to the bypass tunnel, maintaining MPLS TE Fast Reroute maintenance traffic protection without relying on global re-routing or IGP convergence. On the Cisco SPCOR 350-501 exam, this scenario tests your understanding of local protection mechanisms versus end-to-end path protection—a common trap is choosing MPLS TE path protection, which requires head-end signaling and is too slow for maintenance windows. Remember the key differentiator: FRR is local and pre-computed, making it ideal for both failures and planned outages. Memory tip: “FRR = Fast, Local, Pre-planned—perfect for maintenance without pain.”
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.
A service provider wants to ensure that customer traffic is not impacted during a planned maintenance on a core LSR in an MPLS network. Which MPLS feature should be used?
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
MPLS TE Fast Reroute (FRR) is the correct feature because it provides local protection against link or node failures by pre-computing backup paths (bypass tunnels) that are activated within 50 milliseconds of a failure. This ensures that customer traffic is not impacted during planned maintenance on a core LSR, as the backup path is already in place and can be triggered by a manual administrative action (e.g., shutting down the interface) to seamlessly redirect traffic before the maintenance begins.
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.
✓
MPLS TE Fast Reroute
Why this is correct
FRR provides sub-50ms protection by pre-computing backup paths.
Related concept
Read the scenario before looking for a memorised answer.
✗
MPLS TTL propagation
Why it's wrong here
TTL propagation is used for traceroute and does not provide protection.
✗
MPLS LDP synchronization
Why it's wrong here
LDP synchronization affects IGP cost when LDP is not yet established, not for maintenance protection.
✗
MPLS OAM
Why it's wrong here
MPLS OAM is for operation, administration, and maintenance, not for traffic protection.
Common exam traps
Common exam trap: answer the scenario, not the keyword
The trap here is that candidates often confuse MPLS TE FRR with MPLS LDP synchronization or MPLS OAM, mistakenly thinking that any 'protection' or 'monitoring' feature can handle planned maintenance, when only FRR provides the sub-50 ms local repair capability required for hitless maintenance.
Detailed technical explanation
How to think about this question
MPLS TE FRR uses two primary backup methods: link protection (via next-hop backup tunnels) and node protection (via next-next-hop backup tunnels), both relying on RSVP-TE to signal the backup LSPs. The backup tunnels are pre-installed in the forwarding table, so when a failure is detected (or manually triggered), the PLR (Point of Local Repair) immediately switches traffic to the bypass tunnel without waiting for IGP convergence. In a real-world scenario, an operator can issue a 'mpls traffic-eng fast-reroute' command on the interface and then administratively bring down the link, causing the PLR to activate the backup path in under 50 ms, ensuring zero packet loss for customer traffic.
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 small business has 20 workstations on the 192.168.1.0/24 network and one public IP from its ISP. The router uses PAT (NAT overload) so all 20 devices share one public address using different source ports. NAT questions test whether you understand the four address terms and which direction each translation applies.
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: MPLS TE Fast Reroute — MPLS TE Fast Reroute (FRR) is the correct feature because it provides local protection against link or node failures by pre-computing backup paths (bypass tunnels) that are activated within 50 milliseconds of a failure. This ensures that customer traffic is not impacted during planned maintenance on a core LSR, as the backup path is already in place and can be triggered by a manual administrative action (e.g., shutting down the interface) to seamlessly redirect traffic before the maintenance begins.
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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