Understanding How The Cisco Unified Ip Phone Interacts With The Cisco Catalyst Family Of Switches - Cisco 7902G 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 Cisco Catalyst Family of Switches
Cisco Unified IP Phone Administration Guide for Cisco Unified CallManager 5.0 (SCCP), Cisco Unified IP Phones
OL-8151-01
Understanding Interactions with Other Cisco Unified Communications Products
The Cisco Unified IP Phone 7912G has an internal Ethernet switch, enabling it to
switch incoming traffic to the phone, to the access port, or to the network port.
The Cisco Unified IP Phone 7902G and 7905G do not include an internal Ethernet
switch or an access port.
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:
The current VLANs may be configured on an IP subnet basis. However,
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additional IP addresses may 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 may reduce the quality
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of Voice-over-IP 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:
Voice traffic to and from the IP phone (auxiliary VLAN)
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Data traffic to and from the PC connected to the switch through the access
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port of the IP phone (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 more information, refer to the documentation included with the
Cisco Catalyst switch.
Related Topics
Network and Access Ports, page 3-3
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Understanding the Phone Startup Process, page 2-4
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Modifying DHCP Settings, page 4-15
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2-3