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Catalyst 3750 Switch Software Configuration Guide
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Chapter 16 Configuring Voice VLAN
Displaying Voice VLAN
Configuring the Priority of Incoming Data Frames
You can connect a PC or other data device to a Cisco IP Phone port. To process tagged data traffic (in
802.1Q or 802.1p frames), you can configure the switch to send CDP packets to instruct the IP phone
how to send data packets from the device attached to the access port on the Cisco IP Phone. The PC can
generate packets with an assigned CoS value. You can configure the Cisco IP Phone to not change (trust)
or to override (not trust) the priority of frames arriving on the IP phone port from connected devices.
Beginning in privileged EXEC mode, follow these steps to set the priority of data traffic received from
the nonvoice port on the Cisco IP Phone:
This example shows how to configure a port connected to an IP phone to not change the priority of
frames received from the PC or the attached device:
Switch# configure terminal
Enter configuration commands, one per line. End with CNTL/Z.
Switch(config)# interface gigabitethernet1/0/1
Switch(config-if)# switchport priority extend trust
Switch(config-if)# end
To return the port to its default setting, use the no switchport priority extend interface configuration
command.
Displaying Voice VLAN
To display voice VLAN configuration for an interface, use the show interfaces interface-id switchport
privileged EXEC command.
Command Purpose
Step 1
configure terminal Enter global configuration mode.
Step 2
interface interface-id Enter interface configuration mode, and specify the interface connected to the
IP phone.
Step 3
switchport priority extend
{cos value | trust}
Set the priority of data traffic received from the IP phone access port:
• cos value—Configure the IP phone to override the priority received from
the PC or the attached device with the specified CoS value. The value is
a number from 0 to 7, with 7 as the highest priority. The default priority
is cos 0.
• trust—Configure the IP phone access port to trust the priority received
from the PC or the attached device.
Step 4
end Return to privileged EXEC mode.
Step 5
show interfaces interface-id
switchport
Verify your entries.
Step 6
copy running-config
startup-config
(Optional) Save your entries in the configuration file.
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