The answer is DSCP 46 (EF) for voice and DSCP 34 (AF41) for video. This is correct because the DiffServ model defines specific Per-Hop Behaviors (PHBs) to handle different traffic sensitivities: voice requires the Expedited Forwarding (EF) PHB, which guarantees low latency, jitter, and loss by placing traffic into a strict priority queue, while video uses Assured Forwarding (AF41), which offers a lower-priority but still preferential treatment over best-effort data, allowing for some packet loss without breaking the stream. On the ENCOR 350-401 exam, this question tests your ability to apply standard DiffServ DSCP markings for voice and video in a converged network design—a common scenario in QoS sections. A frequent trap is confusing AF41 (DSCP 34) with AF31 (DSCP 26) or using CS3 (DSCP 24), which lack the drop-precedence guarantees video needs. Memory tip: think “EF = Express First” for voice, and for video remember “AF41 = 4-1” (class 4, low drop), which maps to DSCP 34.
350-401 Enterprise Network Design Practice Question
This 350-401 practice question tests your understanding of enterprise network design. 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.
A network architect is designing QoS for a converged network carrying voice, video, and data. The design must use the DiffServ model and ensure that voice traffic is marked with the highest priority and that video traffic is marked with a lower priority but still above data. Which DSCP markings should be assigned to voice and video traffic, respectively, to comply with the standard Per-Hop Behavior (PHB) definitions?
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Voice: DSCP 46 (EF); Video: DSCP 34 (AF41)
Option A is correct because the DiffServ model defines specific Per-Hop Behaviors (PHBs) for different traffic types. Voice traffic requires low latency, jitter, and loss, which is best served by the Expedited Forwarding (EF) PHB, assigned DSCP 46. Video traffic, while still delay-sensitive, can tolerate some loss and is typically marked with Assured Forwarding (AF41, DSCP 34), which provides a lower priority queue than EF but higher than best-effort data.
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.
✓
Voice: DSCP 46 (EF); Video: DSCP 34 (AF41)
Why this is correct
EF (DSCP 46) provides strict priority for voice; AF41 (DSCP 34) provides assured forwarding for video with lower priority than voice.
Related concept
Read the scenario before looking for a memorised answer.
✗
Voice: DSCP 56 (CS7); Video: DSCP 48 (CS6)
Why it's wrong here
CS7 and CS6 are reserved for network control traffic (e.g., routing protocols), not for user traffic like voice and video.
✗
Voice: DSCP 40 (AF41); Video: DSCP 46 (EF)
Why it's wrong here
This reverses the priorities: video would get strict priority (EF) and voice would get assured forwarding, which is incorrect.
✗
Voice: DSCP 26 (AF31); Video: DSCP 18 (AF21)
Why it's wrong here
AF31 and AF21 are lower priority than EF and AF41; voice requires the highest priority (EF), not assured forwarding.
Common exam traps
Common exam trap: answer the scenario, not the keyword
Cisco often tests the specific DSCP values for EF (46) and AF41 (34) and the fact that voice must use EF (not AF or CS) to ensure strict priority queuing, while video uses the highest AF class (AF41) to differentiate it from data without breaking the EF queue.
Detailed technical explanation
How to think about this question
The EF PHB (RFC 3246) is designed for low-loss, low-latency, low-jitter services and is implemented using a strict priority queue (LLQ) in Cisco routers. The AF PHB (RFC 2597) defines four classes (AF1x–AF4x) with three drop precedences each; AF41 (DSCP 34) is the highest-priority AF class, suitable for video that can tolerate occasional packet drops but still requires bandwidth guarantees. In a real-world deployment, mis-marking voice as AF41 could cause voice quality degradation during congestion, as AF traffic is policed and subject to WRED, unlike EF which is typically policed at the edge and given strict priority.
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.
Related glossary terms
Concepts from this question explained
These glossary pages explain the core terms tested in this 350-401 question in full detail.
Enterprise Network Design — This question tests Enterprise Network Design — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: Voice: DSCP 46 (EF); Video: DSCP 34 (AF41) — Option A is correct because the DiffServ model defines specific Per-Hop Behaviors (PHBs) for different traffic types. Voice traffic requires low latency, jitter, and loss, which is best served by the Expedited Forwarding (EF) PHB, assigned DSCP 46. Video traffic, while still delay-sensitive, can tolerate some loss and is typically marked with Assured Forwarding (AF41, DSCP 34), which provides a lower priority queue than EF but higher than best-effort data.
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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