The answer is multi-segment PW (MS-PW) with backup, along with PW redundancy with active/standby and PW protection via TE tunnels. MS-PW with backup is valid because it extends pseudowire protection across multiple MPLS domains or areas by establishing a primary switched path and a separate backup path; if the primary MS-PW fails, traffic seamlessly switches to the backup, ensuring end-to-end service continuity without relying on a single LSP. On the Cisco SPCOR 350-501 exam, this concept tests your understanding of how pseudowire protection methods differ from simple link or node protection—common traps include confusing MS-PW backup with mere LSP redundancy or assuming that all forms of FRR apply to pseudowires. Remember that MS-PW backup is specifically designed for multi-segment scenarios, while PW redundancy with active/standby handles single-segment failover. A useful memory tip: “MS-PW backup protects the path across segments; active/standby protects the endpoint.”
350-501 Services Practice Question
This 350-501 practice question tests your understanding of services. 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.
Which three of the following are valid methods for protecting a pseudowire in an MPLS network?
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Multi-segment PW with backup
Multi-segment PW (MS-PW) with backup is a valid protection method because it allows a pseudowire to be established across multiple MPLS segments, with a backup PW path that can take over if the primary MS-PW fails. This provides end-to-end pseudowire redundancy by using a secondary switched path, ensuring service continuity in multi-domain or multi-area MPLS networks.
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.
✓
Multi-segment PW with backup
Why this is correct
Correct. Multi-segment pseudowires can be configured with a backup path for redundancy.
Related concept
Read the scenario before looking for a memorised answer.
✗
Ethernet OAM CFM
Why it's wrong here
Incorrect. Ethernet OAM detects link issues but does not provide pseudowire protection.
✓
RSVP FRR for link protection
Why this is correct
Correct. Fast Reroute can protect the underlying MPLS TE tunnel carrying the pseudowire.
Related concept
Read the scenario before looking for a memorised answer.
✓
PW redundancy with active/standby
Why this is correct
Correct. PW redundancy provides a backup pseudowire that is used upon failure.
Related concept
Read the scenario before looking for a memorised answer.
✗
LSP ping for fault detection
Why it's wrong here
Incorrect. LSP ping is used for connectivity verification, not protection switching.
Common exam traps
Common exam trap: answer the scenario, not the keyword
Cisco often tests the distinction between fault detection tools (like LSP ping or Ethernet OAM) and actual protection mechanisms (like FRR or PW redundancy), leading candidates to mistakenly select detection methods as valid protection answers.
Detailed technical explanation
How to think about this question
Pseudowire protection in MPLS often leverages mechanisms like PW redundancy (active/standby) defined in RFC 6718, where the standby PW is pre-signaled and can be activated upon failure detection via BGP or LDP. RSVP FRR (Fast Reroute) protects the underlying LSP at the link or node level by pre-computing a backup tunnel, which indirectly protects the pseudowire if it is transported over that LSP, but this does not provide PW-level redundancy. In real-world deployments, combining PW redundancy with MPLS-TP or segment routing can offer sub-50ms failover for critical services like mobile backhaul.
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.
Services — This question tests Services — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: Multi-segment PW with backup — Multi-segment PW (MS-PW) with backup is a valid protection method because it allows a pseudowire to be established across multiple MPLS segments, with a backup PW path that can take over if the primary MS-PW fails. This provides end-to-end pseudowire redundancy by using a secondary switched path, ensuring service continuity in multi-domain or multi-area MPLS networks.
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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