300-070 · Question #102
By default, what value is voice traffic marked as on a Cisco Catalyst Switch?
The correct answer is A. DSCP EF value 46, Cos 5. Quality of Service (QoS) markings ensure voice traffic receives priority treatment across the network. By default on Cisco Catalyst switches, voice (RTP media) traffic is marked with: DSCP EF (Expedited Forwarding) with a value of 46, and a Layer 2 CoS (Class of Service) value…
Question
By default, what value is voice traffic marked as on a Cisco Catalyst Switch?
Options
- ADSCP EF value 46, Cos 5.
- BDSCP EF value 46, Cos 7.
- CDSCP CAS6 value 21, Cos 3.
- DDSCP AF21, Cos 5.
How the community answered
(28 responses)- A89% (25)
- B7% (2)
- C4% (1)
Explanation
Quality of Service (QoS) markings ensure voice traffic receives priority treatment across the network. By default on Cisco Catalyst switches, voice (RTP media) traffic is marked with: DSCP EF (Expedited Forwarding) with a value of 46, and a Layer 2 CoS (Class of Service) value of 5. DSCP EF 46 is the industry-standard DSCP marking for voice bearer traffic per RFC 3246, ensuring it receives the lowest latency and jitter treatment. CoS 5 is the corresponding Layer 2 802.1p priority tag for voice. Call signaling traffic (e.g., SCCP, SIP) is typically marked DSCP CS3/AF31 with CoS 3. The other options are incorrect: CoS 7 (answer B) is reserved for network control traffic; DSCP CAS6/21 and AF21 (answers C and D) are markings for video or transactional data, not voice.
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