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Cisco Systems, Inc. www.cisco.com
Configuring Voice VLAN
Information About Configuring Voice VLAN
Voice VLAN
The voice VLAN feature enables access ports to carry IP voice traffic from an IP phone. When the switch is connected
to a Cisco 7960 IP Phone, the phone sends voice traffic with Layer 3 IP precedence and Layer 2 class of service (CoS)
values, which are both set to 5 by default. Because the sound quality of a Cisco IP phone call can deteriorate if the data
is unevenly sent, the switch supports quality of service (QoS) based on IEEE 802.1p CoS. QoS uses classification and
scheduling to send network traffic from the switch in a predictable manner. Voice VLAN is referred to as an auxiliary VLAN
in some switch documentation.
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 a Cisco IP phone.
The Cisco IP phone contains an integrated three-port 10/100 switch as shown in Figure 35 on page 310. 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.
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