The correct answer is that the policy-map type is not supported because it is being applied to an interface that does not support hierarchical QoS (HQoS). On Cisco IOS-XR platforms, certain physical interfaces—such as Ethernet ports or bundle interfaces—cannot directly accept a service-policy that contains a child policy-map; they require the policy-map to be nested under a parent policy-map at the interface level. This error often appears when using NETCONF/YANG automation, where the configuration syntax is valid but the device rejects it due to hardware or software capability constraints. On the Cisco SPCOR 350-501 exam, this scenario tests your understanding of QoS hierarchy and interface-level limitations, with a common trap being that students assume the error is due to a YANG model mismatch or NETCONF protocol issue. Remember: if the error says “not supported on interface location,” think HQoS—physical interfaces need a parent, not a child. A useful memory tip is “No child on a physical tile—nest it in a parent file.”
350-501 Automation and Quality of Service Practice Question
This 350-501 practice question tests your understanding of automation and quality of service. 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 service provider uses a centralized automation system to manage QoS policies via NETCONF and YANG. When attempting to push a new policy-map, the device returns an error indicating that the policy-map type is not supported in the specified location. 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 policy-map is being applied to an interface that does not support hierarchical QoS
The error indicates that the policy-map type is not supported in the specified location. This typically occurs when a policy-map is applied to an interface that does not support hierarchical QoS (HQoS), such as a physical interface that requires a service-policy under a parent policy-map. The NETCONF/YANG operation succeeds in syntax but fails due to device-level capability constraints.
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 YANG module for QoS is not installed on the device
Why it's wrong here
If the module were missing, the NETCONF request would fail with a different error, such as 'module not found'.
✗
The NETCONF session is not authenticated
Why it's wrong here
Authentication issues would prevent any NETCONF operations from proceeding.
✗
The automation system is using the wrong namespace
Why it's wrong here
A namespace mismatch would cause an XML parsing error, not a policy-type error.
✓
The policy-map is being applied to an interface that does not support hierarchical QoS
Why this is correct
Some interface types, like tunnel interfaces, do not support hierarchical QoS policies; applying one results in this error.
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.
Common exam traps
Common exam trap: answer the scenario, not the keyword
Cisco often tests the distinction between YANG schema validation and device capability enforcement, leading candidates to incorrectly blame namespace or module issues when the real problem is a hardware or software feature limitation.
Detailed technical explanation
How to think about this question
Hierarchical QoS (HQoS) allows nested policy-maps where a child policy-map (e.g., for shaping or queuing) is applied under a parent policy-map (e.g., for policing). On Cisco IOS XR, the parent policy-map must be applied to the interface, and the child policy-map must be defined within the parent using the 'service-policy' command. If the child policy-map is directly applied to an interface that does not support HQoS, the device rejects it with a 'policy-map type not supported' error. NETCONF/YANG operations validate schema but not device-specific feature support, so this error surfaces only at commit time.
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 policy-map is being applied to an interface that does not support hierarchical QoS — The error indicates that the policy-map type is not supported in the specified location. This typically occurs when a policy-map is applied to an interface that does not support hierarchical QoS (HQoS), such as a physical interface that requires a service-policy under a parent policy-map. The NETCONF/YANG operation succeeds in syntax but fails due to device-level capability constraints.
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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