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15-3
Catalyst 3750-E and 3560-E Switch Software Configuration Guide
OL-9775-02
Chapter 15 Configuring Voice VLAN
Configuring Voice VLAN
Note 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.
Configuring Voice VLAN
These sections contain this configuration information:
• Default Voice VLAN Configuration, page 15-3
• Voice VLAN Configuration Guidelines, page 15-3
• Configuring a Port Connected to a Cisco 7960 IP Phone, page 15-4
Default Voice VLAN Configuration
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.
Voice VLAN Configuration Guidelines
These are the voice VLAN configuration guidelines:
• You should configure voice VLAN on switch access ports; voice VLAN is not supported on
trunk ports. You can configure a voice VLAN only on Layer 2 ports.
Note Voice VLAN is only supported on access ports and not on trunk ports, even though the
configuration is allowed.
• 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 Chapter 13, “Configuring
VLANs,” 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 “Configuring a Power Management
Mode on a PoE Port” section on page 11-26.
• 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 Chapter 36, “Configuring QoS.”
• 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.)