Quick Answer
The answer is DSCP EF, which stands for Expedited Forwarding and corresponds to a per-hop behavior value of 46. This marking is correct for voice traffic because it guarantees strict priority queuing across the network, minimizing the latency, jitter, and packet loss that real-time voice payloads require, as defined by RFC 3246. On the Cisco SPCOR / CCNP Service Provider Core 350-501 exam, this question tests your understanding of end-to-end QoS prioritization and the specific DSCP markings for different traffic classes; a common trap is confusing voice payload (EF) with voice signaling (CS3 or AF31). Remember that DSCP EF is the only marking that maps directly to the priority queue on Cisco routers, ensuring that voice packets are serviced before any other traffic. A simple memory tip: think of EF as “Expedite First” for voice, since voice must be handled before anything else to maintain call quality.
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.
An engineer is configuring QoS for voice traffic on a Cisco router. Which marking should be applied to voice packets to ensure proper end-to-end prioritization?
DSCP AF41
Why wrong: DSCP AF41 is used for multimedia conferencing, not voice.
DSCP CS3
Why wrong: DSCP CS3 is for broadcast video, not voice.
DSCP EF
DSCP EF is the correct marking for voice payload.
IP Precedence 3
Why wrong: IP Precedence 3 corresponds to DSCP 24, typically used for voice signaling.
Answer choices
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
DSCP EF
Voice traffic requires low latency, jitter, and packet loss. DSCP EF (Expedited Forwarding, per-hop behavior value 46) is the standard marking for real-time voice payloads, ensuring strict priority queuing (PQ) across the network. RFC 3246 defines EF for this purpose, and Cisco routers use it to map voice to the priority queue.
Key principle: Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Answer analysis
For each option: why learners choose it and why it is or isn't the right answer here.
DSCP AF41
Why it's wrong here
DSCP AF41 is used for multimedia conferencing, not voice.
DSCP CS3
Why it's wrong here
DSCP CS3 is for broadcast video, not voice.
DSCP EF
Why this is correct
DSCP EF is the correct marking for voice payload.
Related concept
Read the scenario before looking for a memorised answer.
IP Precedence 3
Why it's wrong here
IP Precedence 3 corresponds to DSCP 24, typically used for voice signaling.
Common exam traps
Cisco often tests the distinction between voice bearer (RTP) and voice signaling (SIP/H.323) markings, so the trap here is that candidates confuse DSCP CS3 (for signaling) with DSCP EF (for actual voice payload), or assume IP Precedence 3 is sufficient despite its lack of strict priority behavior.
Detailed technical explanation
Under the hood, DSCP EF sets the 6-bit Differentiated Services Code Point to 101110 (binary), which corresponds to a per-hop behavior that guarantees a minimum departure rate and low jitter. In real-world deployments, voice packets marked EF are placed into a strict priority queue (LLQ) on Cisco routers, while other traffic (e.g., AF41 for video, CS3 for signaling) uses separate bandwidth queues. Mis-marking voice as AF41 could cause it to compete with video or data during congestion, leading to unacceptable delay.
Key takeaway
Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Real-world example
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
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Automation and Quality of Service — study guide chapter
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FAQ
Automation and Quality of Service — This question tests Automation and Quality of Service — Read the scenario before looking for a memorised answer..
The correct answer is: DSCP EF — Voice traffic requires low latency, jitter, and packet loss. DSCP EF (Expedited Forwarding, per-hop behavior value 46) is the standard marking for real-time voice payloads, ensuring strict priority queuing (PQ) across the network. RFC 3246 defines EF for this purpose, and Cisco routers use it to map voice to the priority queue.
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
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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