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Catalyst 2950 and Catalyst 2955 Switch Software Configuration Guide
OL-10101-02
Chapter 18 Configuring Voice VLAN
Configuring Voice VLAN
Figure 18-1 Cisco 7960 IP Phone Connected to a Switch
When the IP Phone connects to the switch, the access port (PC-to-telephone jack) of the IP phone can
connect to a PC. Packets to and from the PC and to or from the IP phone share the same physical link to
the switch and the same switch port. For deployment examples that use voice VLANs, see the
“Network
Configuration Examples” section on page 1-11.
Configuring Voice VLAN
This section describes how to configure voice VLAN on access ports. It contains this configuration
information:
• Default Voice VLAN Configuration, page 18-2
• Voice VLAN Configuration Guidelines, page 18-3
• Configuring a Port to Connect to a Cisco 7960 IP Phone, page 18-3
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 default CoS value is 0 for incoming traffic.
The CoS value is not trusted for IEEE 802.1p or IEEE 802.1Q tagged traffic.
The IP Phone overrides the priority of all incoming traffic (tagged and untagged) and sets the CoS value
to 0.
Note In software releases earlier than Cisco IOS Release 12.1(13)EA1, the CoS value is trusted for all IEEE
802.1p or IEEE 802.1Q tagged traffic, and the IP Phone does not override the priority of the incoming
traffic.
3-port
switch
P1 P3
P2
Access
port
Cisco IP Phone 7960
PC
101351
Phone
ASIC