How to Configuring Cisco IP Phone Voice Traffic

   Configuring Cisco IP Phone Voice Traffic

You can configure a port connected to the Cisco IP Phone to send CDP packets to the phone to configure the way in which the phone sends voice traffic. The phone can carry voice traffic in IEEE 802.1Q frames for a specified voice VLAN with a Layer 2 CoS value. It can use IEEE 802.1p priority tagging to give voice traffic a higher priority and forward all voice traffic through the native (access) VLAN. The Cisco IP Phone can also send untagged voice traffic or use its own configuration to send voice traffic in the access VLAN. In all configurations, the voice traffic carries a Layer 3 IP precedence value (the default is 5).

Beginning in privileged EXEC mode, follow these steps to configure voice traffic on a port:

Steps	Command	Purpose
Step 1	configure terminal	Enter global configuration mode.
Step 2	interface interface-id	Specify the interface connected to the phone, and enter interface configuration mode.
Step 3	mls qos trust cos	Configure the interface to classify incoming traffic packets by using the packet CoS value. For untagged packets, the port default CoS value is used. Note Before configuring the port trust state, you must first globally enable QoS by using the mls qos global configuration command.
Step 4	switchport  voice {detectcisco-phone [full-duplex] | vlan {vlan-id |dot1p | none |untagged}}	Configure how the Cisco IP Phone carries voice traffic: •detect—Configure the interface to detect and recognize a Cisco IP phone. •cisco-phone—When you initially implement the switchport voice detect command, this is the only allowed option. The default is no switchport voice detect cisco-phone [full-duplex]. •full-duplex—(Opti onal) Configure the switch to only accept a full-duplex Cisco IP phone. •vlan-id—Configure the phone to forward all voice traffic through the specified VLAN. By default, the Cisco IP Phone forwards the voice traffic with an IEEE 802.1Q priority of 5. Valid VLAN IDs are 1 to 4094. •dot1p—Configure the phone to use IEEE 802.1p priority tagging for voice traffic and to use the default native VLAN (VLAN 0) to carry all traffic. By default, the Cisco IP Phone forwards the voice traffic with an IEEE 802.1p priority of 5. •none—Allow the phone to use its own configuration to send untagged voice traffic. •untagged—Configure the phone to send untagged voice traffic.
Step 5	end	Return to privileged EXEC mode.
Step 6	show interfacesinterface-id switchportor show running-config interface interface-id	Verify your voice VLAN entries. Verify your QoS and voice VLAN entries.
Step 7	copy running-config startup-config	(Optional) Save your entries in the configuration file.

This example shows how to configure a port connected to a Cisco IP Phone to use the CoS value to classify incoming traffic, to use IEEE 802.1p priority tagging for voice traffic, and to use the default native VLAN (VLAN 0) to carry all traffic:

Switch# configure terminal

Enter configuration commands, one per line. End with CNTL/Z.

Switch(config)# interface gigabitethernet0/1

Switch(config-if)# mls qos trust cos

Switch(config-if)# switchport voice vlan dot1p

Switch(config-if)# end

To return the port to its default setting, use the no switchport voice vlan interface configuration command.

This example shows how to enable switchport voice detect on a Cisco IP Phone:

Switch# configure terminal

Enter configuration commands, one per line. End with CNTL/Z.

Switch(config)# interface fastethernet 0/1

Switch(config-if)# switchport voice?

detect                         detection enhancement keyword

vlan                           VLAN for voice traffic

Switch(config-if)# switchport voice detect?

cisco-phone                           Cisco IP Phone

Switch(config-if)# switchport voice detect cisco-phone?

full-duplex                           Cisco IP Phone

Switch(config-if)# switchport voice detect cisco-phone full-duplex

full-duplex                           full duplex keyword

Switch(config-if)# end

This example shows how to disable switchport voice detect on a Cisco IP Phone:

Switch# configure terminal

Enter configuration commands, one per line. End with CNTL/Z.

Switch(config)# interface fastethernet 0/1

Switch(config-if)# no switchport voice detect cisco-phone

Switch(config-if)# no switchport voice detect cisco-phone full-duplex

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 IEEE 802.1Q or IEEE 802.1p frames), you can configure the switch to send CDP packets to instruct the 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 phone to not change (trust) or to override (not trust) the priority of frames arriving on the 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:

	Command	Purpose
Step 1	configure terminal	Enter global configuration mode.
Step 2	interfaceinterface-id	Specify the interface connected to the Cisco IP Phone, and enter interface configuration mode.
Step 3	switchport priority extend {cos value | trust}	Set the priority of data traffic received from the Cisco IP Phone access port: •cos value—Configure the 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 cos0. •trust—Configure the 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 interfacesinterface-idswitchport	Verify your entries.
Step 6	copy running-config startup-config	(Optional) Save your entries in the configuration file.

This example shows how to configure a port connected to a Cisco 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 gigabitethernet0/1

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.