Configuring Voice Switch Ports
Command Meaning
mls qos Configured from global configuration mode, this command
enables globally on the switch the feature set to run QOS.
switchport voice vlan This configures a switch port association into a voice VLAN.
The voice VLAN used to be called an auxiliary VLAN and allows
an access port to be associated to a data and voice VLAN
simultaneously.
mls qos trust cos This configures a switch port to trust the frame’s COS priority
tag. If a frame is untagged, then the port’s default COS value will
be used.
switchport priority
extend cos
Configures the switchport to override or rewrite the 802.1p (COS)
value that is in an incoming frame’s header. This is establishing
your QOS policy at the edge or your network. With regard to
QOS, the edge of the network is also called the trust boundary.
switchport priority
extend trust
This configures the switchport to trust or leave the 802.1p (COS)
value that is in an incoming frame’s header. This is establishing
your QOS policy at the edge or your network. With regard to
QOS, the edge of the network is also called the trust boundary.
mls qos trust device
cisco-phone
This configures the switchport to trust the priority marking coming
from the Cisco phone. This configuration will work only with
a Cisco phone because the switch and the phone communicate
using CDP.
OK, here goes, this is the hardest part of the book, but take a look at how I did it and try
it for yourself if possible:
Switch#configure t
Switch(config)#mls qos
Switch(config)#interface f0/1
Switch(config-if)#switchport priority extend ?
cos Override 802.1p priority of devices on appliance
trust Trust 802.1p priorities of devices on appliance
Switch(config-if)#switchport priority extend trust
Switch(config-if)#mls qos trust cos
Switch(config-if)#switchport voice vlan dot1p
Switch(config-if)#switchport mode access
Switch(config-if)#switchport access vlan 3
Switch(config-if)#switchport voice vlan 10
The command mls qos trust cos will configure the interface to classify incoming traffic
packets by using the packet CoS value. For untagged packets, the port’s default CoS value will
be used. But before configuring the port trust state, you must first globally enable QoS by
using the mls qos global configuration command.