- A
DSCP values can be set at the PE router to classify customer traffic into different classes.
PE routers can mark DSCP for customer traffic before entering the MPLS backbone.
- B
MPLS EXP bits can be used to prioritize traffic across the service provider backbone.
EXP bits are the standard way to carry QoS across MPLS.
- C
QoS policies cannot be applied to MPLS interfaces due to label encapsulation.
Why wrong: QoS policies can be applied to MPLS interfaces, often using EXP-based classification.
- D
802.1p CoS marking is preserved across the MPLS backbone by default.
Why wrong: 802.1p is typically not preserved across MPLS backbone without explicit mapping.
- E
Hierarchical QoS (HQoS) can be used to apply per-VPN QoS policies on a PE router.
HQoS allows separate policies for different VPNs on the same interface.
Quick Answer
The answer is that Hierarchical QoS (HQoS) can be used to apply per-VPN QoS policies on a PE router. This is correct because HQoS allows a service provider to enforce separate traffic contracts for each customer VPN on a single physical interface, using a two-level scheduler that shapes and prioritizes traffic at both the aggregate and per-VPN level. In the context of the Cisco SPCOR 350-501 exam, this concept tests your understanding of how QoS implementation in an MPLS VPN environment integrates DSCP marking at the ingress edge with EXP bit mapping across the MPLS core, where HQoS is the key mechanism for granular control on PE routers. A common trap is confusing HQoS with simple interface-level shaping, but remember that HQoS is specifically designed to manage multiple queues per VPN. Memory tip: think of HQoS as "VPN-level policing with a parent-child scheduler" to distinguish it from flat QoS.
350-501 Automation and Quality of Service Practice Question
This 350-501 practice question tests your understanding of automation and quality of service. Read the scenario carefully and evaluate each option against the stated constraints before committing to an answer. 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.
Which THREE statements about implementing QoS in an MPLS VPN environment are correct? (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
DSCP values can be set at the PE router to classify customer traffic into different classes.
Option A is correct because on a PE router, DSCP values can be set or remarked to classify incoming customer traffic into distinct service classes. This classification is performed at the ingress edge of the MPLS VPN network, allowing the provider to apply appropriate per-hop behaviors (PHBs) before the traffic is label-switched.
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.
- ✓
DSCP values can be set at the PE router to classify customer traffic into different classes.
Why this is correct
PE routers can mark DSCP for customer traffic before entering the MPLS backbone.
Related concept
Read the scenario before looking for a memorised answer.
- ✓
MPLS EXP bits can be used to prioritize traffic across the service provider backbone.
Why this is correct
EXP bits are the standard way to carry QoS across MPLS.
Related concept
Read the scenario before looking for a memorised answer.
- ✗
QoS policies cannot be applied to MPLS interfaces due to label encapsulation.
Why it's wrong here
QoS policies can be applied to MPLS interfaces, often using EXP-based classification.
- ✗
802.1p CoS marking is preserved across the MPLS backbone by default.
Why it's wrong here
802.1p is typically not preserved across MPLS backbone without explicit mapping.
- ✓
Hierarchical QoS (HQoS) can be used to apply per-VPN QoS policies on a PE router.
Why this is correct
HQoS allows separate policies for different VPNs on the same interface.
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 misconception that MPLS encapsulation prevents QoS application, when in fact QoS policies are fully supported on MPLS interfaces, and the trap is that 802.1p CoS is not automatically preserved across the MPLS backbone—it must be explicitly mapped to MPLS EXP bits.
Detailed technical explanation
How to think about this question
MPLS EXP bits (3 bits) provide up to 8 classes of service within the MPLS label stack, analogous to IP DSCP (6 bits) but with coarser granularity. In a typical MPLS VPN deployment, the PE router maps the customer's DSCP or 802.1p markings to MPLS EXP bits at ingress, and the P routers perform QoS based solely on these EXP bits. Hierarchical QoS (HQoS) on the PE allows per-VPN shaping and policing by nesting a child policy (per-VPN class) under a parent policy (physical interface), enabling granular control without affecting other VPNs.
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.
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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: DSCP values can be set at the PE router to classify customer traffic into different classes. — Option A is correct because on a PE router, DSCP values can be set or remarked to classify incoming customer traffic into distinct service classes. This classification is performed at the ingress edge of the MPLS VPN network, allowing the provider to apply appropriate per-hop behaviors (PHBs) before the traffic is label-switched.
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.
About these practice questions
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Last reviewed: Jun 11, 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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