Cisco 7800 Series Administration Manual page 27

About the Cisco IP Phone
Network Protocol
Cisco Audio Session Tunneling
(CAST)
Cisco Discovery Protocol (CDP)
Domain Name Server (DNS)
Dynamic Host Configuration
Protocol (DHCP)
Purpose
The CAST protocol allows IP
phones and associated applications
behind the phone to discover and
communicate with the remote
endpoints without requiring
changes to the traditional signaling
components like Cisco Unified
Communications Manager and
gateways. The CAST protocol
allows separate hardware devices
to synchronize related media and it
allows PC applications to augment
nonvideo-capable phones to
become video enabled using the PC
as the video resource.
CDP is a device-discovery protocol
that runs on all Cisco-manufactured
equipment.
A device can use CDP to advertise
its existence to other devices and
receive information about other
devices in the network.
DNS translates domain names to
IP addresses.
DHCP dynamically allocates and
assigns an IP address to network
devices.
DHCP enables you to connect an
IP phone into the network and have
the phone become operational
without the need to manually assign
an IP address or to configure
additional network parameters.
Cisco IP Phone 7800 Series Administration Guide for Cisco Unified Communications Manager
Network Protocols
Usage Notes
The Cisco IP Phone uses CAST as
an interface between CUVA and
Cisco Unified Communications
Manager using the Cisco IP Phone
as a SIP proxy.
The Cisco IP Phone uses CDP to
communicate information such as
auxiliary VLAN ID, per port power
management details, and Quality
of Service (QoS) configuration
information with the Cisco Catalyst
switch.
Cisco IP Phones have a DNS client
to translate domain names into IP
addresses.
DHCP is enabled by default. If
disabled, you must manually
configure the IP address, subnet
mask, gateway, and a TFTP server
on each phone locally.
We recommend that you use DHCP
custom option 150. With this
method, you configure the TFTP
server IP address as the option
value. For additional supported
DHCP configurations, see the
documentation for your particular
Cisco Unified Communications
Manager release.
Note If you cannot use option
150, use DHCP option
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