Cisco IE 4000, Software Configuration Manual

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Configuring Voice VLAN
Information About Configuring Voice VLAN
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

Voice VLAN configuration is only supported on switch access ports; voice VLAN configuration is not supported on
trunk ports.
Note: 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).

Before you enable voice VLAN, we recommend that you enable QoS on the switch. If you use the auto-QoS feature,
these settings are automatically configured. For more information, see
Configuring QoS, page 571

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.)

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 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 IEEE 802.1p or untagged frames.
— The Cisco IP phone uses IEEE 802.1p frames, and the device uses untagged frames.
— The Cisco IP phone uses untagged frames, and the device uses IEEE 802.1p frames.
— The Cisco IP phone uses IEEE 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.

Voice VLAN ports can also be these port types:
— Dynamic access port.
— IEEE 802.1x authenticated port. See Configuring IEEE 802.1x Port-Based Authentication, page 189 for more
information.
If you enable IEEE 802.1x on an access port on which a voice VLAN is configured and to which a Cisco IP phone
is connected, the phone loses connectivity to the switch for up to 30 seconds.
— Protected port.
— A source or destination port for a SPAN or RSPAN session.
— Secure port.