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38-2
Software Configuration Guide—Release 15.0(2)SG
OL-23818-01
Chapter 38 Configuring Voice Interfaces
About Voice Interfaces
The Cisco 7960 IP Phone contains an integrated three-port 10/100 switch. The ports are dedicated
connections as described below:
• Port 1 connects to the Catalyst 4500 series switch or other device that supports voice-over-IP.
• Port 2 is an internal 10/100 interface that carries the phone traffic.
• Port 3 connects to a PC or other device.
Figure 38-1 shows one way to configure a Cisco 7960 IP Phone.
Figure 38-1 Cisco 7960 IP Phone Connected to a Catalyst 4500 Series Switch
Cisco IP Phone Voice Traffic
You can configure an access port with an attached Cisco IP phone to use one VLAN for voice traffic and
another VLAN for data traffic from a device attached to the phone. You can configure access ports on
the switch to send Cisco Discovery Protocol (CDP) packets that instruct an attached phone to send voice
traffic to the switch in any of these ways:
• In the voice VLAN tagged with a Layer 2 CoS priority value
• In the access VLAN tagged with a Layer 2 CoS priority value
• In the access VLAN, untagged (no Layer 2 CoS priority value)
Note In all configurations, the voice traffic carries a Layer 3 IP precedence value (the default is 5 for voice
traffic and 3 for voice control traffic).
Cisco IP Phone Data Traffic
The switch can also process tagged data traffic (traffic in IEEE 802.1Q or IEEE 802.1p frame types)
from the device attached to the access port on the Cisco IP phone. See Figure 38-1. 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 using the access port on the Cisco IP phone passes using the
phone unchanged.
• In untrusted mode, all traffic in IEEE 802.1Q or IEEE 802.1p frames received using 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 phone passes using the phone unchanged,
regardless of the trust state of the access port on the phone.
IP Phone
Catalyst 4500 Series Switch
PC
105247
IP