What command configures a port with a voice VLAN using 802.1Q?

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The command that configures a port with a voice VLAN using 802.1Q is switchport voice vlan 10. This configuration uses 802.1Q as a default. 802.1P is configured with the command switchport voice vlan 10 dot1p . These are the only two valid commands to configure voice VLANs on a switch port.

The following is an example of voice VLAN configuration and QoS:

switch(config)# mls qos
switch(config)# interface fastethernet 0/10
switch(config-if)# switchport voice vlan 100
switch(config-if)# switchport access vlan 1
switch(config-if)# switchport priority extend trust
switch(config-if)# mls qos trust cos
switch(config-if)# mls qos trust device cisco-phone

In this example, the mls qos command enables QoS on the switch. The interface command moves the administrator into interface configuration mode. The switchport voice vlan 100 command configures the voice VLAN to be 100 using 802.1Q. If you wanted 802.1P, the command would have been switchport voice vlan 100 dot1p .

The VLAN for data traffic is defined with the fourth command, switchport access vlan 1 . The switchport priority extend trust command instructs the port to trust the CoS of the data traffic being passed from a PC connected to the IP phone. The mls qos trust cos command tells the port to use the CoS value of traffic passed to it from the phone or PC to classify traffic. (It is included here for illustration purposes only, as this command is not necessary when using the switchport priority extend trust command since the CoS value of the PC will be trusted anyway.) The mls qos trust device cisco-phone command tells the port to trust the QoS information provided from the IP phone if it is a Cisco phone.

The other options are incorrect due to invalid syntax.

Objective:
Layer 2 Technologies
Sub-Objective:
Configure and verify VLANs