Cisco Systems 3750E manual Cisco IP Phone Voice Traffic, Cisco IP Phone Data Traffic, 15-2

Chapter 15 Configuring Voice VLAN

Understanding Voice VLAN

Figure 15-1shows one way to connect a Cisco 7960 IP Phone.

Figure 15-1 Cisco 7960 IP Phone Connected to a Switch

Cisco IP Phone 7960

Phone

ASIC

P2

P1 3-port P3 switch Access

port

PC

101351

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 15-1). 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 through the access port on the Cisco IP Phone passes through the phone unchanged.

•In untrusted mode, all traffic in IEEE 802.1Q or IEEE 802.1p frames received through 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.

Catalyst 3750-E and 3560-E Switch Software Configuration Guide

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