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Cisco IE 2000 Switch Software Configuration Guide
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Chapter 19 Configuring Voice VLAN
Information About Configuring Voice VLAN
Cisco IP Phone Data Traffic
The switch can also process tagged data traffic (traffic in IEEE 802.1Q or IEEE 802.1p frame ty pes) from
the device attached to the access port on the Cisco IP phone (see Figure 19-1). You can configure Layer 2
access ports on the switch to send CDP packets that instruct the attached phone to configure the phone
access port in one of these modes:
In trusted mode, all traffic received through the access port on the Cisco IP phone passes through
the phone unchanged.
In untrusted mode, all traffic in IEEE 802.1Q or IEEE 802.1p f rames received through the access
port on the Cisco IP phone receive a configured Layer 2 CoS value. The default Layer 2 CoS value
is 0. Untrusted mode is the default.
Note Untagged traffic from the device attached to the Cisco IP ph one passes through the phone unchanged,
regardless of the trust state of the access port on the phone.
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). If the VLAN is not listed, see Chapter 17, “Configuring
VLANs,” for information on how to create the voice VLAN.
Before you enable voice VLAN, we recommend that you enable QoS on the sw itch 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 sett ings are
automatically configured. For more information, see Chapter 38, “Configuring Standard 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.)
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: