The answer is that the 'Policy map not found' error in a hierarchical QoS configuration is caused by a missing child policy-map that the parent policy references via its 'service-policy' command. This occurs because hierarchical QoS requires both a parent policy (typically a shaper) and a child policy (containing CBWFQ classes) to exist as separate, named policy-maps; when the parent tries to nest the child, the router cannot find the child object in its running configuration, triggering the error. On the Cisco SPCOR / CCNP Service Provider Core 350-501 exam, this scenario tests your understanding of the strict dependency between parent and child policy-maps in hierarchical QoS—a common trap is assuming the parent policy alone is sufficient, or confusing the error with a missing interface-level policy. A useful memory tip is to think of it as a "nested doll" problem: if the inner doll (child policy) isn't created, the outer doll (parent policy) cannot close, so always verify the child policy-map name matches exactly before applying the parent.
350-501 Automation and Quality of Service Practice Question
This 350-501 practice question tests your understanding of automation and quality of service. This is a configuration task: choose the command set that satisfies every stated requirement. Small differences — like 'secret' vs 'password' or 'transport input ssh' vs 'all' — change whether the answer is correct. 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.
An SP router is configured with a hierarchical QoS policy (parent policy shaper, child policy with CBWFQ). When applying this policy to an interface, the router reports 'Policy map not found' error. What is the most likely cause?
Clue words in this question
Noticing these words before you look at the options changes how you read each choice.
Clue: "most likely"
Why it matters: Probability qualifier — the question wants the most probable cause or outcome, not a guaranteed one. Eliminate low-probability options.
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
The child policy-map specified in the parent's 'service-policy' command does not exist.
The 'Policy map not found' error occurs when the parent policy-map references a child policy-map via the 'service-policy' command, but that child policy-map does not exist in the router's configuration. Hierarchical QoS requires both the parent and child policy-maps to be created and correctly named; a missing child policy-map prevents the router from applying the nested policy.
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.
✗
The interface speed is not configured.
Why it's wrong here
Interface speed is auto-negotiated; error would be different.
The child policy-map specified in the parent's 'service-policy' command does not exist.
Why this is correct
The child policy must exist before applying the parent.
Clue confirmation
The clue word "most likely" in the question point toward this answer.
Related concept
Read the scenario before looking for a memorised answer.
✗
The shape average command in the parent policy uses an unsupported value.
Why it's wrong here
Shape average values are checked at commit; this error message is specific.
Common exam traps
Common exam trap: answer the scenario, not the keyword
Cisco often tests the distinction between configuration errors (e.g., missing policy-map) and operational errors (e.g., unsupported values), leading candidates to overthink interface or shaping parameters when the actual issue is a simple missing object.
Detailed technical explanation
How to think about this question
Hierarchical QoS (HQoS) on Cisco IOS XR or IOS XE uses a parent policy-map to shape traffic and a child policy-map to apply CBWFQ queuing. The parent's 'service-policy child' command must reference an existing child policy-map; if it is misspelled or not yet created, the router cannot parse the nested structure and returns the 'Policy map not found' error. In real-world deployments, this often happens when copying configurations between devices without ensuring all referenced policy-maps are present.
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 practitioner preparing for the 350-501 exam encounters this exact type of scenario on the job. The correct answer here is not the most general option — it is the best answer for the specific constraint described. Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option. Real exam questions reward reading the full scenario before eliminating options, because the constraint defines which answer fits.
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.
Automation and Quality of Service — This question tests Automation and Quality of Service — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: The child policy-map specified in the parent's 'service-policy' command does not exist. — The 'Policy map not found' error occurs when the parent policy-map references a child policy-map via the 'service-policy' command, but that child policy-map does not exist in the router's configuration. Hierarchical QoS requires both the parent and child policy-maps to be created and correctly named; a missing child policy-map prevents the router from applying the nested policy.
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.
Are there clue words in this question I should notice?
Yes — watch for: "most likely". Probability qualifier — the question wants the most probable cause or outcome, not a guaranteed one. Eliminate low-probability options.
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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