Cisco 7609 User Manual

11-2
Cisco 7600 Series Router Cisco IOS Software Configuration Guide—12.1E
78-14064-04
Chapter 11 Configuring Cisco IP Phone Support
Understanding Cisco IP Phone Support
Figure 11-1 Cisco IP Phone Connected to a Switch
Cisco IP Phone Voice Traffic
The Cisco IP Phone transmits voice traffic with Layer 3 IP precedence and Layer 2 CoS values, which
are both set to 5 by default. The sound quality of a Cisco IP Phone call can deteriorate if the voice traffic
is transmitted unevenly. To provide more predictable voice traffic flow, you can configure QoS to trust the
Layer 3 IP precedence or Layer 2 CoS value in the voice traffic (refer to Chapter 32, “Configuring PFC
QoS”).
Note You can configure the ports on WS-X6548-RJ-45 and WS-X6548-RJ-21 switching modules to trust
received Layer 2 CoS values (QoS port architecture 1p1q0t/1p3q1t). The WS-X6548-RJ-45 and
WS-X6548-RJ-21 switching modules cannot supply power to Cisco IP Phones. Configure QoS policies
that use the Layer 3 IP precedence value on other switching modules.
You can configure a Layer 2 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 Cisco IP Phone.
You can configure Layer 2 access ports on the router to send Cisco Discovery Protocol version 2
(CDPv2) packets that instruct an attached Cisco IP Phone to transmit voice traffic to the switch in any
of the following 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).
You cannot use Cisco IOS software commands to configure the frame type used by data traffic sent from
a device attached to the access port on the Cisco IP Phone.
3-port
switch
P1
P3
P2
Access
port
Cisco IP Phone 7960
Workstation/PC
Catalyst switch or
Cisco Router
10/100 module
79490
Phone
ASIC

Cisco 7609 Specifications

General

Brand	Cisco
Model	7609
Category	Network Router
Language	English