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15-2
Catalyst 2940 Switch Software Configuration Guide
78-15507-02
Chapter 15 Configuring Voice VLAN
Configuring Voice VLAN
Figure 15-1 shows one way to connect a Cisco 7960 IP Phone.
Figure 15-1 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, refer to the
“Network Configuration Examples” section on page 1-7.
Configuring Voice VLAN
This section describes how to configure voice VLAN on access ports. It contains this configuration
information:
• Default Voice VLAN Configuration, page 15-2
• Voice VLAN Configuration Guidelines, page 15-3
• Configuring a Port to Connect to a Cisco 7960 IP Phone, page 15-3
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 802.1P or 802.1Q tagged traffic.
The IP Phone overrides the priority of all incoming traffic (tagged and untagged) and sets the CoS
value to 0.
3-port
switch
P1 P3
P2
Access
port
Cisco IP Phone 7960
PC
Catalyst 2940
switch
87828
Phone
ASIC