- A
Apply a flat QoS policy on the core interfaces that polices each DSCP value to a fixed rate; trust is not needed because the core enforces its own limits.
Why wrong: Flat policing on core cannot enforce per-customer contracts and does not prevent customer remarking from affecting other customers.
- B
Use auto-qos on all PE interfaces and rely on CoS trust; the core uses MPLS EXP derived from CoS to ensure proper queuing.
Why wrong: Auto-qos does not offer per-customer traffic separation and trust is already compromised by customers remarking DSCP.
- C
Implement hierarchical QoS on the PE egress to customer-facing interfaces, with parent-level shaping per customer and child-level policing per class, and set a trust boundary to mark all traffic based on the customer contract at ingress.
Hierarchical QoS provides both per-customer and per-class enforcement, and setting trust boundary at ingress solves the remarking issue.
- D
Configure MPLS Traffic Engineering tunnels on the core with bandwidth reservation per customer class; use EXP-null to preserve markings end-to-end.
Why wrong: TE tunnels provide bandwidth but do not solve the trust boundary issue; remarking still requires trust boundary at PE.
Quick Answer
The answer is to implement hierarchical QoS on the PE egress to customer-facing interfaces, with parent-level shaping per customer and child-level policing per class, while enforcing a strict trust boundary to re-mark all traffic at ingress based on the per-customer contract. This design is correct because hierarchical QoS creates a two-level policy where the parent enforces per-customer bandwidth guarantees to prevent starvation, and the child policies apply per-class policing for voice, video, and data, directly addressing the broken trust boundary where customers were remarking DSCP values. On the Cisco SPCOR 350-501 exam, this scenario tests your understanding of how to combine trust boundary enforcement with scalable per-customer QoS using the MQC hierarchy, a common trap being to confuse flat policies or MPLS TE tunnels which lack per-customer granularity. Remember the memory tip: “Parent shapes the pipe, child polices the class, and ingress marks the trust.”
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 experiencing congestion on a core link connecting two P routers. The customer traffic is classified into three classes: voice (low latency), video (low loss), and data (best effort). The current configuration uses DSCP-based classification at the PE ingress, but many customers are remarking DSCP values to gain better service, bypassing the provider's QoS policy. The provider wants to enforce a strict trust boundary at the PE and re-mark all traffic according to a per-customer contract. Additionally, the provider must offer per-customer bandwidth guarantees, ensuring that one customer's traffic does not starve another customer's traffic on the congested core link. The solution must be scalable to hundreds of customers. What should the designer recommend?
Clue words in this question
Noticing these words before you look at the options changes how you read each choice.
Clue:
"best"Why it matters: Signals that multiple options may be partially correct. Choose the option that most directly solves the exact problem described, not the one that sounds most complete.
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
Implement hierarchical QoS on the PE egress to customer-facing interfaces, with parent-level shaping per customer and child-level policing per class, and set a trust boundary to mark all traffic based on the customer contract at ingress.
Option A is correct because hierarchical QoS allows per-customer shaping at the parent level to enforce per-customer bandwidth limits, and per-class policing at the child level to enforce per-class contracts. This provides the required trust boundary and per-customer guarantees. Option B is wrong because auto-qos does not provide per-customer granularity and relies on trust which is already broken. Option C is wrong because MPLS TE tunnels reserve bandwidth but do not solve the trust boundary issue; also resetting EXP is complex. Option D is wrong because a flat policy on core does not allow per-customer differentiation and cannot enforce per-customer guarantees.
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.
- ✗
Apply a flat QoS policy on the core interfaces that polices each DSCP value to a fixed rate; trust is not needed because the core enforces its own limits.
Why it's wrong here
Flat policing on core cannot enforce per-customer contracts and does not prevent customer remarking from affecting other customers.
- ✗
Use auto-qos on all PE interfaces and rely on CoS trust; the core uses MPLS EXP derived from CoS to ensure proper queuing.
- ✓
Implement hierarchical QoS on the PE egress to customer-facing interfaces, with parent-level shaping per customer and child-level policing per class, and set a trust boundary to mark all traffic based on the customer contract at ingress.
Why this is correct
Hierarchical QoS provides both per-customer and per-class enforcement, and setting trust boundary at ingress solves the remarking issue.
Clue confirmation
The clue word "best" in the question point toward this answer.
Related concept
Read the scenario before looking for a memorised answer.
- ✗
Configure MPLS Traffic Engineering tunnels on the core with bandwidth reservation per customer class; use EXP-null to preserve markings end-to-end.
Why it's wrong here
TE tunnels provide bandwidth but do not solve the trust boundary issue; remarking still requires trust boundary at PE.
Common exam traps
Common exam trap: answer the scenario, not the keyword
Many certification questions include familiar terms but test a specific constraint. Read the exact wording before choosing an answer that is generally true but wrong for this case.
Detailed technical explanation
How to think about this question
This question should be treated as a scenario, not a definition check. Identify the problem, the constraint and the best action. Then compare each option against those facts.
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.
- Use explanations to understand the rule behind the answer.
TExam Day Tips
- Underline the problem statement mentally.
- 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 350-501 exam domain this question belongs to, then review the specific concept being tested. Practise related questions in that domain and focus on understanding why each wrong answer is tempting — not just why the correct answer is right.
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Automation and Quality of Service — study guide chapter
Learn the concepts, then practise the questions
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Automation and Quality of Service practice questions
Targeted practice on this topic area only
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All 350-501 questions
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Cisco SPCOR / CCNP Service Provider Core 350-501 study guide
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350-501 practice test guide
How to use practice tests most effectively before exam day
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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: Implement hierarchical QoS on the PE egress to customer-facing interfaces, with parent-level shaping per customer and child-level policing per class, and set a trust boundary to mark all traffic based on the customer contract at ingress. — Option A is correct because hierarchical QoS allows per-customer shaping at the parent level to enforce per-customer bandwidth limits, and per-class policing at the child level to enforce per-class contracts. This provides the required trust boundary and per-customer guarantees. Option B is wrong because auto-qos does not provide per-customer granularity and relies on trust which is already broken. Option C is wrong because MPLS TE tunnels reserve bandwidth but do not solve the trust boundary issue; also resetting EXP is complex. Option D is wrong because a flat policy on core does not allow per-customer differentiation and cannot enforce per-customer guarantees.
What should I do if I get this 350-501 question wrong?
Identify which 350-501 exam domain this question belongs to, then review the specific concept being tested. Practise related questions in that domain and focus on understanding why each wrong answer is tempting — not just why the correct answer is right.
Are there clue words in this question I should notice?
Yes — watch for: "best". Signals that multiple options may be partially correct. Choose the option that most directly solves the exact problem described, not the one that sounds most complete.
What is the key concept behind this question?
Read the scenario before looking for a memorised answer.
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Last reviewed: Jun 24, 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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