The correct answer is that the nested service-policy under shape applies the INNER_POLICY to traffic after shaping, enabling per-class queuing within the shaped rate. This works because the shape command creates a traffic policer or shaper at 10 Mbps, and the nested service-policy then operates on the shaped output, allowing you to define class-based actions like bandwidth guarantees or priority queuing for specific traffic types inside that 10 Mbps envelope. On the ENCOR 350-401 exam, this tests your understanding of Hierarchical QoS (HQoS), where the outer policy shapes the aggregate and the inner policy manages per-class treatment—a common trap is confusing the order of operations, thinking the inner policy applies before shaping. Remember the memory tip: “Shape the pipe, then queue the classes inside the pipe.”
CCNP QoS Architecture Practice Question
This 350-401 practice question tests your understanding of qos architecture. 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.
Examine the following configuration:
policy-map SHAPE_POLICY
class class-default
shape average 10000000
service-policy INNER_POLICY
What is the purpose of the nested service-policy (service-policy INNER_POLICY) under the shape command?
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
It applies the INNER_POLICY to traffic after shaping, allowing per-class queuing within the shaped rate.
The correct answer is A because the nested service-policy under the shape command applies the INNER_POLICY to traffic after it has been shaped to 10 Mbps. This allows per-class queuing and scheduling within the shaped rate, enabling finer QoS control such as bandwidth allocation or priority queuing for specific traffic classes while ensuring the overall output does not exceed the shaped rate.
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.
✓
It applies the INNER_POLICY to traffic after shaping, allowing per-class queuing within the shaped rate.
Why this is correct
Hierarchical QoS: the inner policy manages queues within the shaped pipe.
Related concept
Read the scenario before looking for a memorised answer.
✗
It applies the INNER_POLICY to traffic before shaping, which is not supported.
Why it's wrong here
The inner policy is applied after shaping; the order is shape then apply inner policy.
✗
It is used to shape traffic twice, first at 10 Mbps and then again based on INNER_POLICY.
Why it's wrong here
The inner policy does not shape; it typically does queuing or policing.
✗
This configuration is invalid because service-policy cannot be nested under shape.
Why it's wrong here
Nesting is valid in Cisco IOS for hierarchical QoS.
Common exam traps
Common exam trap: answer the scenario, not the keyword
Cisco often tests the concept that a nested service-policy under shape applies after shaping, not before, and that it is a valid method for hierarchical QoS, leading candidates to incorrectly assume it is unsupported or that it shapes traffic twice.
Detailed technical explanation
How to think about this question
This configuration implements hierarchical QoS (HQoS), where the outer shape command enforces a maximum transmission rate of 10 Mbps, and the inner service-policy (INNER_POLICY) defines per-class queuing behaviors (e.g., bandwidth guarantees, priority) within that shaped rate. Under the hood, the shaping process uses a token bucket to meter traffic, and the nested policy applies to the shaped output queue, allowing class-based scheduling such as low-latency queuing (LLQ) or weighted fair queuing (WFQ). In real-world scenarios, this is critical for ensuring voice traffic gets priority within a subscriber's shaped rate without exceeding the contracted bandwidth.
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 350-401 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.
QoS Architecture — This question tests QoS Architecture — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: It applies the INNER_POLICY to traffic after shaping, allowing per-class queuing within the shaped rate. — The correct answer is A because the nested service-policy under the shape command applies the INNER_POLICY to traffic after it has been shaped to 10 Mbps. This allows per-class queuing and scheduling within the shaped rate, enabling finer QoS control such as bandwidth allocation or priority queuing for specific traffic classes while ensuring the overall output does not exceed the shaped rate.
What should I do if I get this 350-401 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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