Trunkports can carry any number of voice VLANs, similar to regular VLANs. The
configurationof voice VLANsis notsupported ontrunk ports.
Note
Beforeyou enable voice VLAN, we recommend that you enable QoS on the switch by entering the mls
qosglobal configuration command and configure the port trust state to trust by entering the mls qos
trustcos interface configuration command. Ifyou use the auto-QoS feature, these settings are
automaticallyconfigured.
Youmust enable CDP on the switch port connected to the Cisco IP Phone to send the configuration to
thephone. (CDP is globally enabled by default on all switch interfaces.)
Restrictions for Voice VLANs
Thefollowing arethe restrictionsfor voice VLANs:
Donot configurevoice VLAN on private VLAN ports.
Youcannot configure static secure MAC addresses in the voice VLAN.
Information About Voice VLAN

Voice VLANs

Thevoice VLAN feature enables access ports to carry IPvoice traffic from an IP phone. When the switch is
connectedto a Cisco 7960 IP Phone, the phone sends voice trafficwith Layer 3 IP precedence and Layer 2
classof service (CoS) values, which are both set to 5 by default. Because the sound quality of an IP phone
callcan deteriorate if the data is unevenly sent, the switch supports quality of service (QoS) based on IEEE
802.1pCoS. QoS uses classificationand scheduling to send network traffic from the switch in a predictable
manner.
TheCisco 7960 IP Phone is a configurable device, and you can configure it to forward traffic with an IEEE
802.1ppriority. You can configure the switch to trust or override the traffic priority assigned by a Cisco
IPPhone.
Thisnetwork configurationis one wayto connecta Cisco7960 IP Phone.
TheCisco IP Phone contains an integrated three-port 10/100 switch. The ports provide dedicated connections
tothese devices:
Port1 connectsto theswitch or othervoice-over-IP (VoIP) device.
Port2 is an internal10/100 interface that carries the IP phone traffic.
Port3 (accessport) connectsto a PCor other device.
Catalyst 2960-XR Switch VLAN Configuration Guide, Cisco IOS Release 15.0(2)EX1
150 OL-29440-01
Configuring Voice VLANs
Restrictions for Voice VLANs