2-3
Cisco Unified IP Phone 7960G and 7940G Administration Guide for Release 8.0 (SIP)
OL-7890-01
Chapter 2 Installing Cisco Unified IP Phone 7960G and 7940G Hardware on the Desktop or Wall
Using the Phone with a Cisco Catalyst Switch
Note
Do not connect the phone to power or the network at this time. Doing so causes the phone to initialize
and download firmware and configuration files. Initialization and modification of the configuration files
are described in the
Chapter 3, “Initializing Cisco Unified IP Phones.”
Using the Phone with a Cisco Catalyst Switch
To function in the SIP telephony network, the Cisco Unified IP Phone 7960G and 7940G must be
connected to a networking device, such as a Cisco Catalyst switch, to obtain network connectivity. The
Cisco IP Phone 7960G/7940G has an internal Ethernet switch, which enables it to switch traffic that
comes from the phone, access port, and network port.
If a computer is connected to the access port, packets that travel to and from the computer and to and
from the phone share the same physical link to the switch and the same port on the switch. This
configuration has the following implications for the VLAN configuration on the network:
•
The current VLANs might be configured on an IP subnet basis, and additional IP addresses might
not be available to assign the phone to the same subnet as other devices (PC) connected to the same
port.
•
Data traffic that is present on the VLAN that supports phones might reduce the quality of VoIP
traffic.
You can resolve these issues by isolating the voice traffic onto a separate VLAN on each of the ports
connected to a phone. The switch port configured for connecting a phone would have separate VLANs
configured for carrying the following traffic:
•
Voice traffic to and from the Cisco Unified IP Phone 7960G and 7940G (auxiliary VLAN).
•
Data traffic to and from the PC connected to the switch through the access port of the
Cisco IP Phone 7960G/7940G (native VLAN).
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 redundancy, you can use the AC adapter even if you are using inline power from the Cisco Catalyst
switches. The Cisco Unified IP Phone 7960G and 7940G can share the power load being used from the
inline power and external power source. If either the inline power or the external power goes down, the
phone can switch entirely to the other power source.
To use this redundancy feature you
must
set the inline power mode to “auto” on the Cisco Catalyst
switch. Next, connect the Cisco Unified IP Phone 7960G and 7940G phone to the network without
connecting it to an external power source. After the phone powers up, connect the external power supply
to the phone.
For more information, refer to the documentation included with the Cisco Catalyst switch.
