Configuring Voice Vlan; Default Voice Vlan Configuration; Voice Vlan Configuration Guidelines - Cisco Catalyst 3750 Software Configuration Manual

Chapter 12

Configuring Voice VLAN

Configuring Voice VLAN
This section describes how to configure voice VLAN on access ports. This section contains this
configuration information:
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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 802.1p or 802.1Q tagged traffic.

Voice VLAN Configuration Guidelines

These are the voice VLAN configuration guidelines:
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78-15870-01
Default Voice VLAN Configuration, page 12-3
Voice VLAN Configuration Guidelines, page 12-3
Configuring a Port Connected to a Cisco 7960 IP Phone, page 12-4
You should configure voice VLAN on switch access ports; voice VLAN is not supported on trunk
ports. You can only configure a voice VLAN on Layer 2 ports.
Voice VLAN is only supported on access ports and not on trunk ports, even though the
Note
configuration is allowed.
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 configuration to
the Cisco IP Phone. (CDP is enabled by default globally and on all switch interfaces.)
The Port Fast feature is automatically enabled when voice VLAN is configured. When you disable
voice VLAN, the Port Fast feature is not automatically disabled.
If the Cisco IP Phone and a device attached to the Cisco IP Phone are in the same VLAN, they must
be in the same IP subnet. These conditions indicate that they are in the same VLAN:
They both use 802.1p or untagged frames.
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– The Cisco IP Phone uses 802.1p frames and the device uses untagged frames.
– The Cisco IP Phone uses untagged frames and the device uses 802.1p frames.
– The Cisco IP Phone uses 802.1Q frames and the voice VLAN is the same as the access VLAN.
The Cisco IP Phone and a device attached to the phone cannot communicate if they are in the same
VLAN and subnet but use different frame types because traffic in the same subnet is not routed
(routing would eliminate the frame type difference).
You cannot configure static secure MAC addresses in the voice VLAN.
Chapter 26, "Configuring QoS."
Catalyst 3750 Metro Switch Software Configuration Guide
Configuring Voice VLAN
12-3