CCNP Architecture Practice Question
A network architect is designing a QoS policy for a Cisco Catalyst switch. The architect needs to ensure that voice traffic is marked with the appropriate DSCP value for expedited forwarding. Which DSCP value should be used for voice traffic?
⚠ Common exam trap
It's easy for candidates to confuse voice payload marking with call signaling marking, or using control traffic DSCP values for voice.
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
✓
EF (46)
Voice traffic should be marked with DSCP EF (46) to ensure expedited forwarding, which provides low latency, jitter, and loss. Other DSCP values like AF31 are used for call signaling, while CS6 and CS7 are reserved for network control. Proper marking ensures that voice packets receive priority treatment in QoS-enabled networks.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
CS7 (56)
Why it's wrong here
CS7 (Class Selector 7) with DSCP value 56 is reserved for network control traffic, such as link-layer keepalives and routing protocols. It is not used for voice. Voice traffic should be marked with EF. Using CS7 for voice would be inappropriate and could disrupt network control functions.
- ✗
CS6 (48)
Why it's wrong here
CS6 (Class Selector 6) with DSCP value 48 is often used for network control traffic, such as routing protocol updates. It is not intended for voice traffic. Voice should be marked with EF. Using CS6 for voice could conflict with control plane traffic and does not provide the same priority treatment as EF.
- ✗
AF31 (26)
Why it's wrong here
AF31 (Assured Forwarding Class 3, Drop Precedence 1) with DSCP value 26 is typically used for call signaling traffic, not voice payload. Voice payload requires EF. Using AF31 for voice would not provide the strict priority needed, potentially causing poor voice quality. AF31 is suitable for less delay-sensitive applications.
- ✓
EF (46)
Why this is correct
EF (Expedited Forwarding) with DSCP value 46 is the standard marking for voice traffic. It provides low latency, low jitter, and low loss, which are critical for voice quality. Voice traffic should be marked with EF to ensure it receives priority treatment in the network. This is a widely accepted best practice.
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JA
Written and reviewed by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
Last reviewed September 2026 · checked against the official Cisco exam blueprint
This 350-401 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 350-401 exam.