Specifications

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Catalyst 2970 Switch Software Configuration Guide
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Chapter 13 Configuring Voice VLAN
Configuring Voice VLAN
• Voice VLAN ports can also be these port types:
– Dynamic access port. See the “Configuring Dynamic-Access Ports on VMPS Clients” section
on page 11-29 for more information.
– 802.1X authenticated port. See the “Configuring 802.1X Authentication” section on page 8-12
for more information.
– Protected port. See the “Configuring Protected Ports” section on page 19-5 for more
information.
– A source or destination port for a SPAN or RSPAN session.
– Secure port. See the “Configuring Port Security” section on page 19-7 for more information.
Note When you enable port security on an interface that is also configured with a voice VLAN,
you must set the maximum allowed secure addresses on the port to two plus the maximum
number of secure addresses allowed on the access VLAN. When the port is connected to a
Cisco IP phone, the IP phone requires up to two MAC addresses. The IP phone address is
learned on the voice VLAN and might also be learned on the access VLAN. Connecting a
PC to the IP phone requires additional MAC addresses.
Configuring a Port Connected to a Cisco 7960 IP Phone
Because a Cisco 7960 IP Phone also supports a connection to a PC or other device, a port connecting the
switch to a Cisco IP Phone can carry mixed traffic. You can configure a port to determine how the IP
phone carries voice traffic and data traffic.
This section includes these topics:
• Configuring IP Phone Voice Traffic, page 13-4
• Configuring the Priority of Incoming Data Frames, page 13-5
Configuring IP Phone Voice Traffic
You can configure a port connected to the Cisco IP Phone to send CDP packets to the phone to configure
the way in which the phone sends voice traffic. The phone can carry voice traffic in 802.1Q frames for
a specified voice VLAN with a Layer 2 CoS value. It can use 802.1P priority tagging to give voice traffic
a higher priority and forward all voice traffic through the native (access) VLAN. The IP phone can also
send untagged voice traffic or use its own configuration to send voice traffic in the access VLAN. In all
configurations, the voice traffic carries a Layer 3 IP precedence value (the default is 5).
Beginning in privileged EXEC mode, follow these steps to configure voice traffic on a port:
Command Purpose
Step 1
configure terminal Enter global configuration mode.
Step 2
interface interface-id Enter interface configuration mode, and specify the interface connected to
the IP phone.
Step 3
mls qos trust cos Configure the interface to classify ingress traffic packets by using the packet
CoS value. For untagged packets, the port default CoS value is used.
Note Before configuring the port trust state, you must first globally enable
QoS by using the mls qos global configuration command.