CHAPT ER
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Catalyst 2950 and Catalyst 2955 Switch Software Configuration Guide
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Configuring Voice VLAN
This chapter describes how to configure the voice VLAN feature on your Catalyst 2950 or Catalyst 2955
switch. Voice VLAN is sometimes referred to as an auxiliary VLAN in the Catalyst 6000 family switch
documentation.
Note For complete syntax and usage information for the commands used in this chapter, see the command
reference for this release.
This chapter consists of these sections:
Understanding Voice VLAN, page 18-1
Configuring Voice VLAN, page 18-2
Displaying Voice VLAN, page 18-6

Understanding Voice VLAN

The voice VLAN feature enables access ports to carry IP voice traffic from an IP phone. The switch can
connect to a Cisco 7960 IP Phone and carry IP voice traffic. Because the sound quality of an IP phone
call can deteriorate if the data is unevenly sent, the switch supports quality of service (QoS) based on
IEEE 802.1p class of service (CoS). QoS uses classification and scheduling to send network traffic from
the switch in a predictable manner. For more information on QoS, see Chapter 29, “Configuring QoS.”
The Cisco 7960 IP Phone is a configurable device, and you can configure it to forward traffic with an
IEEE 802.1p priority. You can configure the switch to trust or override the traffic priority assigned by an
IP Phone.
The Cisco 7960 IP Phone contains an integrated three-port 10/100 switch as shown in Figure 18-1. The
ports provide dedicated connections to these devices:
Port 1 connects to the switch or other voice-over-IP (VoIP) device.
Port 2 is an internal 10/100 interface that carries the IP phone traffic.
Port 3 (access port) connects to a PC or other device.
Figure 18-1 shows one way to connect a Cisco 7960 IP Phone.