210-065 Question #108: Real Exam Question with Answer & Explanation

The correct answer is C: signaling and media traffic marked with Layer 2 CoS and Layer 3 DSCP mappings. Proper voice prioritization over data requires marking signaling and media traffic with Layer 2 CoS (802.1p) and Layer 3 DSCP values so that network devices can honor QoS treatment end-to-end.

Question

Which action ensures prioritization of voice over data traffic?

Options

Avoice and data VLAN on different subnets with QoS classification
Bvoice and data VLAN on same subnets without QoS classification
Csignaling and media traffic marked with Layer 2 CoS and Layer 3 DSCP mappings
Dsignaling and media traffic marked with Layer 2 DSCP and Layer 3 CoS mappings

Explanation

Proper voice prioritization over data requires marking signaling and media traffic with Layer 2 CoS (802.1p) and Layer 3 DSCP values so that network devices can honor QoS treatment end-to-end.

Common mistakes.

A. Separate VLANs and subnets with QoS classification help segment traffic but do not by themselves guarantee prioritization without marking - classification alone does not enforce scheduling or queuing.
B. Placing voice and data on the same subnet without QoS classification provides no mechanism to differentiate or prioritize voice traffic over competing data flows.
D. This option reverses the layer associations - DSCP belongs to Layer 3 (IP header) and CoS belongs to Layer 2 (Ethernet frame); swapping them describes an incorrect and non-functional configuration.

Concept tested. Layer 2 CoS and Layer 3 DSCP marking for voice QoS

Reference. https://www.cisco.com/c/en/us/td/docs/ios-xml/ios/qos_classn/configuration/xe-16/qos-classn-xe-16-book/qos-classn-mrkg-map.html

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