Cisco WS-C2950SX-48-SI Configuration Manual page 221

Chapter 10 Configuring VLANs
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Note The Cisco IP Phone always sets Layer 3 IP precedence to 5 in voice traffic.
Auxiliary VLAN Configuration Guidelines
This section describes the guidelines for configuring auxiliary VLANs:
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Configuring Auxiliary VLANs
To configure auxiliary VLANs, perform this task in privileged mode:
Task
Configure auxiliary VLANs.
This example shows how to add voice ports to auxiliary VLANs, specify an encapsulation type, or
specify that the VLAN will not send or receive CDP messages with voice-related information:
Console> (enable) set port auxiliaryvlan 2/1-3 222
Auxiliaryvlan 222 configuration successful.
AuxiliaryVlan AuxVlanStatus Mod/Ports
------------- ------------- -------------------------
222
Console> (enable) set port auxiliaryvlan 5/7 untagged
Port 5/7 allows the connected device send and receive untagged packets and without 802.1p
priority.
Console> (enable) set port auxiliaryvlan 5/9 dot1p
Port 5/9 allows the connected device send and receive packets with 802.1p priority.
Console> (enable) set port auxiliaryvlan 5/12 none
Port 5/12 will not allow sending CDP packets with Voice VLAN information.
Console> (enable)
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802.3 frames, which are untagged and carry no VLAN ID and no Layer 2 CoS value (enter the set
port auxiliaryvlan mod[/port] untagged command)
The IP phone and a device that is attached to the phone are in the same VLAN and must be in the
same IP subnet if one of the following occurs:
– They use the same frame type.
– The phone uses 802.1p frames, and the device uses untagged frames.
– The phone uses untagged frames, and the device uses 802.1p frames.
The phone uses 802.1Q frames, and the auxiliary VLAN equals the native VLAN.
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The IP phone and a device that is attached to the phone cannot communicate if they are in the same
VLAN and subnet but use different frame types, because traffic between devices in the same subnet
is not routed (routing would eliminate the frame type difference).
You cannot use switch commands to configure a frame type that is used by traffic received from a
device attached to the phone's access port.
With software release 6.2(1) and later releases, dynamic ports can belong to two VLANs—a native
VLAN and an auxiliary VLAN. See
VMPS," for configuration details for auxiliary VLANs.
active
Catalyst 4500 Series, Catalyst 2948G, Catalyst 2980G Switches Software Configuration Guide
Chapter 12, "Configuring Dynamic VLAN Membership with
Command
set port auxiliaryvlan mod[/ports] {vlan |
untagged | dot1p | none}
1/2,2/1-3
Configuring Auxiliary VLANs
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Release 8.1
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