The correct answer is to apply a policy-map that matches voice traffic using a class-map and the 'set dscp ef' action. This is correct because, in an MPLS VPN environment, the PE router must mark IP packets at the ingress edge before MPLS encapsulation occurs; the 'set dscp ef' command explicitly sets the DSCP field to EF (46) for matched voice traffic, ensuring that the MPLS core can prioritize these packets based on the EXP bits derived from the DSCP value. On the Cisco SPCOR 350-501 exam, this tests your understanding of QoS marking at the service provider edge, a common scenario where candidates must distinguish between marking before the MPLS core versus after. A frequent trap is assuming that MPLS EXP marking alone is sufficient, but the question specifically requires DSCP marking on the IP header before core entry. Memory tip: think “Edge EF” — always set DSCP EF at the ingress edge of the PE before the MPLS label is pushed.
350-501 Automation and Quality of Service Practice Question
This 350-501 practice question tests your understanding of automation and quality of service. Match the stated requirement to the specific cloud service, access model, or configuration option — many options are valid in isolation but not for this scenario. 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 needs to prioritize voice traffic over best-effort data in an MPLS VPN. The PE router uses a QoS policy applied to the ingress interface. Which action ensures that voice packets are marked with the correct DSCP value before entering the MPLS core?
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 the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Apply a policy-map that matches voice traffic using a class-map and the 'set dscp ef' action.
Option A is correct because the question specifies that the PE router must mark voice packets with the correct DSCP value before they enter the MPLS core. The 'set dscp ef' action in a policy-map applied to the ingress interface explicitly sets the DSCP field to EF (46) for voice traffic matched by a class-map, ensuring proper classification and treatment across the MPLS network. This is the standard method for marking IP packets at the edge before MPLS encapsulation.
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 policy-map that matches voice traffic using a class-map and the 'set dscp ef' action.
Apply a police action to drop traffic exceeding the voice bandwidth.
Why it's wrong here
Policing does not mark packets; it only enforces rate limits.
Common exam traps
Common exam trap: answer the scenario, not the keyword
Cisco often tests the distinction between IP-layer marking (DSCP) and MPLS-layer marking (EXP), so the trap here is that candidates may choose 'set mpls experimental 5' thinking it achieves the same result, but the question explicitly requires DSCP marking before MPLS encapsulation.
Detailed technical explanation
How to think about this question
In MPLS VPN environments, DSCP marking at the ingress PE is critical because the MPLS core typically maps DSCP to EXP bits for QoS treatment; if the DSCP is not set correctly, voice packets may be treated as best-effort. The 'set dscp ef' action uses the DiffServ Code Point value 46 (Expedited Forwarding) per RFC 3246, which ensures low latency, low jitter, and low loss for voice traffic. A real-world scenario involves a service provider that must override customer markings to enforce a consistent QoS policy across the MPLS backbone, making explicit marking essential.
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: Apply a policy-map that matches voice traffic using a class-map and the 'set dscp ef' action. — Option A is correct because the question specifies that the PE router must mark voice packets with the correct DSCP value before they enter the MPLS core. The 'set dscp ef' action in a policy-map applied to the ingress interface explicitly sets the DSCP field to EF (46) for voice traffic matched by a class-map, ensuring proper classification and treatment across the MPLS network. This is the standard method for marking IP packets at the edge before MPLS encapsulation.
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: "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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Question Discussion
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