Table Of Contents

Configuring Voice Interfaces

Configuring a Port to Connect to a Cisco 7690 IP Phone

Configuring Voice Ports to Carry Voice and Data Traffic on Different VLANs

Overriding the CoS Priority of Incoming Frames

Configuring Inline Power

Configuring Voice Interfaces

---

This chapter describes how to configure voice interfaces for the Catalyst 4000 family switches. Catalyst 4000 family switches can connect to a Cisco 7960 IP Phone and carry IP voice traffic. If necessary, the switch can supply electrical power to the circuit connecting it to the Cisco 7960 IP Phone.

Because the sound quality of an IP telephone call can deteriorate if the data is unevenly sent, the switch uses quality of service (QoS) based on IEEE 802.1p class of service (CoS). QoS uses classification and scheduling to transmit network traffic from the switch in a predictable manner. See "Understanding and Configuring QoS" for more information on QoS.

You can configure the Cisco 7960 IP Phone to forward traffic with an 802.1p priority. You can use the CLI to configure a Catalyst 4000 family switch to honor or ignore a traffic priority assigned by a Cisco 7960 IP Phone.

The Cisco 7960 IP Phone contains an integrated three-port 10/100 switch. The ports are dedicated connections as described below:

•Port 1 connects to the Catalyst 4000 family switch or other device that supports voice-over-IP.

•Port 2 is an internal 10/100 interface that carries the phone traffic.

•Port 3 connects to a PC or other device.

Figure 27-1 shows one way to configure a Cisco 7960 IP Phone.

Figure 27-1 Cisco 7960 IP Phone Connected to a Catalyst 4000 Family Switch

Configuring a Port to Connect to a Cisco 7690 IP Phone

Because a Cisco 7960 IP Phone also supports connection to a PC or other device, an interface connecting a Catalyst 4000 family switch to a Cisco 7960 IP Phone can carry a mix of voice and data traffic.

There are three configurations for a port connected to a Cisco 7960 IP Phone:

•All traffic is transmitted according to the default COS priority of the port. This is the default.

•Voice traffic is given a higher priority by the phone, and all traffic is in the same VLAN.

•Voice and data traffic are carried on separate VLANs, and voice traffic always has a CoS priority of 5.

To configure a port to instruct the phone to give voice traffic a higher priority and to forward all traffic through the 802.1Q native VLAN, perform the following procedure beginning in privileged EXEC mode:

	Task	Command
Step 1	Enter configuration mode.	Switch# configure terminal
Step 2	Specify the interface to configure.	Switch(config)# interface {fastethernet | gigabitethernet} slot/port
Step 3	Instruct the switch to use 802.1p priority tagging for voice traffic and to use VLAN 1 (default native VLAN) to carry all traffic.	Switch(config-if)# switchport voice vlan dot1p
Step 4	Return to privileged EXEC mode.	Switch(config-if)# end
Step 5	Verify the port configuration.	Switch# show interface {fastethernet | gigabitethernet} slot/port switchport

Configuring Voice Ports to Carry Voice and Data Traffic on Different VLANs

Because voice and data traffic can travel through the same voice port, you should specify a different VLAN for each type of traffic. You can configure a switch port to forward voice and data traffic on different VLANs.

Beginning in privileged EXEC mode, perform the following procedure to configure a port to receive voice and data from a Cisco IP Phone on different VLANs:

	Task	Command
Step 1	Enter configuration mode.	Switch# configure terminal
Step 2	Specify the interface to configure.	Switch(config)# interface {fastethernet | gigabitethernet} slot/port
Step 3	Instruct the Cisco IP Phone to forward all voice traffic through a specified VLAN. The Cisco IP Phone forwards the traffic with an 802.1p priority of 5.	Switch(config-if)# switchport voice vlan vlan_num
Step 4	Return to privileged EXEC mode.	Switch(config-if)# end
Step 5	Verify the configuration.	Switch# show interface {fastethernet | gigabitethernet} slot/port switchport

In the following example, VLAN 1 carries data traffic, and VLAN 2 carries voice traffic. In this configuration, we must connect all Cisco IP Phones and other voice-related devices to switch ports that belong to VLAN 2.

Switch# configure terminal

Switch(config)# interface fastethernet 2/5 

SSwitch(config-if)# switchport voice vlan 2

switchport voice vlan 2

Switch(config-if)# end

Switch# show interface fastethernet 2/5 switchport

show interface fastethernet 2/5 switchport

Name:Fa2/5

Switchport:Enabled

Administrative Mode:dynamic auto

Operational Mode:down

Administrative Trunking Encapsulation:negotiate

Negotiation of Trunking:On

Access Mode VLAN:1 (default)

Trunking Native Mode VLAN:1 (default)

Voice VLAN:2 ((Inactive))

Appliance trust:none

Administrative private-vlan host-association:none 

Administrative private-vlan mapping:none 

Operational private-vlan:none 

Trunking VLANs Enabled:ALL

Pruning VLANs Enabled:2-1001

Switch#

Overriding the CoS Priority of Incoming Frames

A PC or other data device can connect to a Cisco 7960 IP Phone port. The PC can generate packets with an assigned CoS value. If you want, you can use the switch CLI to override the priority of frames arriving on the phone port from connected devices. You can also set the phone port to accept (trust) the priority of frames arriving on the port.

To override the CoS priority setting received from the non-voice port on the Cisco 7960 IP Phone, perform the following procedure beginning in privileged EXEC mode:

	Task	Command
Step 1	Enter configuration mode.	Switch# configure terminal
Step 2	Specify the interface to configure.	Switch(config)# interface {fastethernet | gigabitethernet} slot/port
Step 3	Set the phone port to override the priority received from the PC or the attached device and forward the received data with a priority of 3. You can use the no keyword to return the port to its default setting.	Switch(config-if)# [no] qos trust extend cos 3
Step 4	Return to privileged EXEC mode.	Switch(config-if)# end
Step 5	Verify the change.	Switch# show interface {fastethernet | gigabitethernet} slot/port switchport

Configuring Inline Power

The Catalyst 4000 family switch can supply inline power to the Cisco 7960 IP Phone, if needed. The Cisco 7960 IP Phone can also be connected to an AC power source and supply its own power to the voice circuit.

The Catalyst 4000 family switch senses if it is connected to a Cisco 7960 IP Phone. If there is no power on the circuit, the switch supplies the power. If there is power on the circuit, the switch does not supply it.

You can configure the switch to never supply power to the Cisco 7960 IP Phone and to disable the detection mechanism. See the "Configuring Inline Power" section for the CLI commands that you use to supply inline power to a Cisco 7960 IP Phone.