During deployment, a network engineer notices that voice traffic is not being tagged correctly as it traverses the network. Which COS to DSCP map must be modified to ensure that voice traffic is treat

Question

Options

• ACOS of 5 to DSCP 46
• BCOS of 7 to DSCP 48
• CCOS of 6 to DSCP 46
• DCOS of 3 to DSCP of 26

• A
  87% (27)
• B
  10% (3)
• C
  3% (1)

Explanation

QoS Mapping: COS to DSCP for Voice Traffic

Voice traffic is standardized to use CoS 5 (Class of Service) at Layer 2 and DSCP 46 (Expedited Forwarding/EF) at Layer 3, making Option A the correct mapping to ensure voice bearer traffic receives low-latency, priority treatment across the network. Option B is incorrect because CoS 7 and DSCP 48 represent network control traffic (like routing protocols), not voice. Option C is wrong because CoS 6 maps to DSCP 48 for internetwork control, and DSCP 46 is not its standard counterpart. Option D is incorrect as CoS 3 with DSCP 26 relates to call signaling or general data traffic classes, not voice media streams.

Memory Tip: Think "5 and 46 keep voices alive" - CoS 5 = DSCP 46 (Expedited Forwarding) is the universal standard for voice bearer (RTP) traffic. If you remember that EF (DSCP 46) is the gold standard for voice, and CoS 5 is its Layer 2 equivalent, you'll never mix them up on exam day.

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