- A
The device has a feature license missing for QoS
Why wrong: Missing licenses typically generate clear error messages and would prevent the policy from being configured.
- B
The device does not support the YANG model used
If the device lacks the required YANG modules, the configuration push may succeed but the policy may not be effective.
- C
The policy was applied to a subinterface but the YANG path specifies a main interface
Applying the policy at the wrong interface hierarchy can result in it not being applied to the intended interface.
- D
The NETCONF transaction was not committed
If the candidate configuration is not committed, the policy is not active on the device.
- E
The policy-map name conflicts with an existing one
Why wrong: A name conflict would cause an error during push, making it obvious.
Quick Answer
The answer is that the NETCONF transaction was not committed, along with YANG model incompatibility and device capability mismatches, as the three primary causes for an automated QoS policy not taking effect. This occurs because Cisco NSO relies on YANG models to translate service definitions into device-specific operations; if the target device does not support the referenced YANG model, the NETCONF or CLI operations will fail silently, leaving the policy unapplied. Additionally, failing to commit the NETCONF transaction means the configuration remains in a candidate datastore and never activates on the device. On the Cisco SPCOR 350-501 exam, this scenario tests your understanding of model-driven orchestration pitfalls, often appearing as a multi-select question where traps include confusing uncommitted transactions with syntax errors. A helpful memory tip is “YANG, Commit, Capability”—always verify the YANG model support, commit the transaction, and confirm device capabilities before assuming the policy is active.
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 is automating QoS policy deployment using Cisco NSO and YANG. During validation, the engineer discovers that the pushed policy is not taking effect. Which three possible causes should be investigated? (Choose three.)
Answer choices
Why each option matters
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
The device does not support the YANG model used
Option B is correct because Cisco NSO uses YANG models to translate service definitions into device-specific CLI or NETCONF operations. If the target device does not support the YANG model referenced in the service package, the NETCONF or CLI operations will fail silently or produce no effect, as the device cannot interpret the configuration intent. This is a common validation failure when using model-driven orchestration with heterogeneous device populations.
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 device has a feature license missing for QoS
Why it's wrong here
Missing licenses typically generate clear error messages and would prevent the policy from being configured.
- ✓
The device does not support the YANG model used
Why this is correct
If the device lacks the required YANG modules, the configuration push may succeed but the policy may not be effective.
Related concept
Read the scenario before looking for a memorised answer.
- ✓
The policy was applied to a subinterface but the YANG path specifies a main interface
Why this is correct
Applying the policy at the wrong interface hierarchy can result in it not being applied to the intended interface.
Related concept
Read the scenario before looking for a memorised answer.
- ✓
The NETCONF transaction was not committed
Why this is correct
If the candidate configuration is not committed, the policy is not active on the device.
Related concept
Read the scenario before looking for a memorised answer.
- ✗
The policy-map name conflicts with an existing one
Why it's wrong here
A name conflict would cause an error during push, making it obvious.
Common exam traps
Common exam trap: answer the scenario, not the keyword
Cisco often tests the distinction between a configuration that is accepted by the device (no commit errors) versus one that actually takes effect, trapping candidates who assume a successful commit means the policy is active.
Detailed technical explanation
How to think about this question
Under the hood, Cisco NSO uses NETCONF or CLI to push YANG-modeled data to devices. When a YANG model is unsupported, the device may accept the NETCONF edit-config but ignore the unknown nodes, or it may reject the entire transaction with an error. In real-world scenarios, this often occurs when using a generic QoS YANG model (e.g., RFC 7317) on a device that only supports a proprietary model (e.g., Cisco-IOS-XE-qos), causing the policy to be silently dropped without any operational effect.
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.
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Automation and Quality of Service — study guide chapter
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FAQ
Questions learners often ask
What does this 350-501 question test?
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 device does not support the YANG model used — Option B is correct because Cisco NSO uses YANG models to translate service definitions into device-specific CLI or NETCONF operations. If the target device does not support the YANG model referenced in the service package, the NETCONF or CLI operations will fail silently or produce no effect, as the device cannot interpret the configuration intent. This is a common validation failure when using model-driven orchestration with heterogeneous device populations.
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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Last reviewed: Jun 25, 2026
This 350-501 practice question is part of Courseiva's free Cisco certification practice question bank. Courseiva provides original exam-style practice questions with explanations, topic-based practice, mock exams, readiness tracking, and study analytics to help learners prepare for the 350-501 exam.
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