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Chapter15 Configuring Voice VLAN
Configuring 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 12-22.
•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 Chapter35, “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.)
•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.
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The Cisco IP Phone uses IEEE 802.1p frames, and the device uses untagged frames.
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The Cisco IP Phone uses untagged frames, and the device uses IEEE 802.1p frames.
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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. See the “Configuring Dynamic-Access Ports on VMPS Clients” section
on page 13-31 for more information.
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IEEE 802.1x authenticated port. See the “Configuring 802.1x Readiness Check” section on
page 10-40 for more information.
Note 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.
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Protected port. See the “Configuring Protected Ports” section on page25-6 for more
information.
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A source or destination port for a SPAN or RSPAN session.
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Secure port. See the “Configuring Port Security” section on page25-9 for more information.