Providing Power To The Cisco Unified Ip Phone - Cisco 7940 - IP Phone VoIP Administration Manual

Chapter 2 Preparing to Install the Cisco Unified IP Phone on Your Network
Understanding How the Cisco Unified IP Phone Interacts with the VLAN
The Cisco Unified IP Phone 7960G and 7940G have an internal Ethernet switch, enabling proper
forwarding of appropriate packets to the phone, to the access port (labeled 10/100 PC on the phone), and
to the network port (labeled 10/100 SW on the phone).
If a computer is connected to the access port, the computer and the phone share the same physical link
to the switch and share the same port on the switch. This shared physical link has the following
implications for the VLAN configuration on the network:
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You can resolve these issues by isolating the voice traffic onto a separate VLAN. The switch port that
the phone is connected to would be configured to have separate VLANs for carrying:
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Isolating the phones on a separate, auxiliary VLAN increases the quality of the voice traffic and allows
a large number of phones to be added to an existing network where there are not enough IP addresses
for each phone.
For more information, refer to the documentation included with a Cisco switch. You can also access
related documentation at this URL:
http://www.cisco.com/univercd/cc/td/doc/product/lan/index.htm
Related Topics
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Providing Power to the Cisco Unified IP Phone

The Cisco Unified IP Phone 7960G and 7940G can be powered with external power or with Power over
Ethernet (PoE). External power is provided through a separate power supply. PoE is provided by a switch
through the Ethernet cable attached to a phone.
Note When you install a phone that is powered with external power, connect the power supply to the phone
and to a power outlet before you connect the Ethernet cable to the phone. When you remove a phone that
is powered with external power, disconnect the Ethernet cable from the phone before you disconnect the
power supply.
Cisco Unified IP Phone 7960G/7940G Administration Guide for Cisco Unified Communications Manager 7.0 (SCCP)
OL-15498-01
The current VLANs might be configured on an IP subnet basis. However, additional IP addresses
might not be available to assign the phone to the same subnet as other devices connected to the same
port.
Data traffic present on the VLAN supporting phones might reduce the quality of Voice-over-IP
traffic.
Network security may indicate a need to isolate the VLAN voice traffic from the VLAN data traffic.
Voice traffic to and from the IP phone (auxiliary VLAN on the Cisco Catalyst 6000 series, for
example)
Data traffic to and from the PC connected to the switch through the access port of the IP phone
(native VLAN)
Understanding the Phone Startup Process, page 2-6
Network and Access Ports, page 3-3
Network Configuration Menu, page 4-4
Providing Power to the Cisco Unified IP Phone
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