Cisco Systems 3560 Manual De Usuario

Untagged traffic from the device attached to the Cisco IP Phone passes through the phone unchanged, 
regardless of the trust state of the access port on the phone.

These sections contain this configuration information:

The voice VLAN feature is disabled by default.

When the voice VLAN feature is enabled, all untagged traffic is sent according to the default CoS 
priority of the port. 

The CoS value is not trusted for IEEE 802.1p or IEEE 802.1Q tagged traffic.

These are the voice VLAN configuration guidelines:

Voice VLAN configuration is only supported on switch access ports; voice VLAN configuration is 
not supported on trunk ports.You can configure a voice VLAN only on Layer 2 ports.

Trunk ports can carry any number of voice VLANs, similar to regular VLANs. The configuration of 
voice VLANs is not required on trunk ports. 

The voice VLAN should be present and active on the switch for the IP phone to correctly 
communicate on the voice VLAN. Use the show vlan privileged EXEC command to see if the 
VLAN is present (listed in the display). If the VLAN is not listed, see 

 for information on how to create the voice VLAN.

Do not configure voice VLAN on private VLAN ports.

The Power over Ethernet (PoE) switches are capable of automatically providing power to Cisco 
pre-standard and IEEE 802.3af-compliant powered devices if they are not being powered by an AC 
power source. For information about PoE interfaces, see the 

.

Before you enable voice VLAN, we recommend that you enable QoS on the switch by entering the 
mls qos global configuration command and configure the port trust state to trust by entering the mls 
qos trust cos interface configuration command. If you use the auto-QoS feature, these settings are 
automatically configured. For more information, see 

You must enable CDP on the switch port connected to the Cisco IP Phone to send the configuration 
to the phone. (CDP is globally enabled by default on all switch interfaces.)