Which command should you issue in interface configuration mode on the Catalyst 2950 switch to make the IP phone trust the CoS priority of incoming data packets generated by the attached host?

Which command should you issue in interface configuration mode on the Catalyst 2950 switch to make the IP phone trust the CoS priority of incoming data packets generated by the attached host?

• A. mls qos trust cos
• B. switchport priority extend trust
• C. mls qos trust extend
• D. switchport priority extend cos

Answer: (B)

Trusting how CoS marks are handled on a port is about where the switch accepts the priority value from inbound frames. When a host is connected through an IP phone, you want the switch to honor the CoS/priority marks carried by the host’s traffic as it passes through the phone and into the switch. The command switchport priority extend trust configures the port to extend that trust boundary to the data path behind the IP phone, so inbound frames from the attached host keep their priority and are mapped to the appropriate QoS queues. This ensures the host’s traffic is treated with the intended priority, matching the CO S markings you expect for data alongside the phone’s voice traffic. Other options either apply general QoS trust without specifically enabling the extension across the IP phone path, or refer to different QoS trust mechanisms that don’t address the required behavior in this scenario.

Trusting how CoS marks are handled on a port is about where the switch accepts the priority value from inbound frames. When a host is connected through an IP phone, you want the switch to honor the CoS/priority marks carried by the host’s traffic as it passes through the phone and into the switch. The command switchport priority extend trust configures the port to extend that trust boundary to the data path behind the IP phone, so inbound frames from the attached host keep their priority and are mapped to the appropriate QoS queues. This ensures the host’s traffic is treated with the intended priority, matching the CO S markings you expect for data alongside the phone’s voice traffic.

Other options either apply general QoS trust without specifically enabling the extension across the IP phone path, or refer to different QoS trust mechanisms that don’t address the required behavior in this scenario.