The correct action is to change the explicit path from 'strict' to 'loose' for the down interface. This works because a strict explicit path in MPLS TE requires every hop to be directly connected; if a specified interface is down, the tunnel cannot form. By marking that hop as loose, the router is allowed to use an alternative next-hop reachable via the IGP, effectively routing around the failed link to reach the next specified node. On the Cisco SPCOR 350-501 exam, this scenario tests your understanding of the difference between strict and loose path options in MPLS TE tunnel configuration—a common trap is assuming you must remove the hop entirely, but the correct fix is to change the hop type. Remember the memory tip: "Strict is strict, loose is cruise"—strict demands direct adjacency, while loose lets the IGP choose the best detour.
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.
A network engineer is troubleshooting an MPLS TE tunnel that is not coming up. The tunnel is configured with a strict explicit path, and the path includes an interface that is currently down. Which action should the engineer take to allow the tunnel to use an alternative path?
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Change the explicit path to 'loose' for the down interface.
Option C is correct because changing the explicit path from 'strict' to 'loose' for the down interface allows the MPLS TE tunnel to use an alternative next-hop that is reachable, even if the specified interface is down. A strict explicit path requires every hop to be directly connected, so a down interface prevents the tunnel from coming up. By making the hop loose, the router can route around the failed link using the IGP's best path to the next specified node.
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.
✗
Increase the path-option preference value.
Why it's wrong here
Preference only orders path-options.
✗
Disable path protection on the tunnel.
Why it's wrong here
Path protection is separate; disabling it does not fix the explicit path issue.
✓
Change the explicit path to 'loose' for the down interface.
Why this is correct
Loose hops allow the tunnel to traverse other interfaces.
Related concept
Read the scenario before looking for a memorised answer.
✗
Configure an affinity constraint to exclude the down interface.
Why it's wrong here
Affinity excludes links but doesn't make the path flexible.
Common exam traps
Common exam trap: answer the scenario, not the keyword
Cisco often tests the distinction between strict and loose explicit paths, where candidates mistakenly think that adjusting path preference or adding constraints can override a strict hop that is down, rather than recognizing that only changing the hop type to loose allows the router to dynamically route around the failure.
Detailed technical explanation
How to think about this question
In MPLS TE, a strict explicit path (using the 'ip explicit-path' command with 'next-address strict') forces each hop to be directly adjacent; if any hop's interface is down, the tunnel cannot signal with RSVP-TE. Changing a hop to 'loose' (via 'next-address loose') instructs the router to use the IGP's shortest path to reach that next node, allowing the tunnel to bypass the failed link. This is similar to how a loose hop in a path computation element (PCE) or segment routing can provide flexibility, but here it is applied directly to the explicit path definition.
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: Change the explicit path to 'loose' for the down interface. — Option C is correct because changing the explicit path from 'strict' to 'loose' for the down interface allows the MPLS TE tunnel to use an alternative next-hop that is reachable, even if the specified interface is down. A strict explicit path requires every hop to be directly connected, so a down interface prevents the tunnel from coming up. By making the hop loose, the router can route around the failed link using the IGP's best path to the next specified node.
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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