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Cisco IE 2000 Switch Software Configuration Guide
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Configuring CDP

Finding Feature Information

Your software release may not support all the features documented in this chapter. For the latest feature
information and caveats, see the release notes for your platform and software release.
Use Cisco Feature Navigator to find information about platform support an d Cisco software image
support. To access Cisco Feature Navigator, go to http://www.cisco.com/go/cfn. An account on
Cisco.com is not required.

Information About CDP

CDP

CDP is a device discovery protocol that runs over Layer 2 (the data link layer) on all Cisco-manufactured
devices (routers, bridges, access servers, and switches) and allows network management applications to
discover Cisco devices that are neighbors of already known devices. With CDP, network management
applications can learn the device type and the Simple Network Ma nagement Protocol (SNMP) agent
address of neighboring devices running lower-layer, transparent protocols. This feature enables
applications to send SNMP queries to neighboring devices.
CDP runs on all media that support Subnetwork Access Protocol (SNAP). Because CD P runs over the
data-link layer only, two systems that support different network-layer protocols can learn about each
other.
Each CDP-configured device sends periodic messages to a multicast address, advertising at least one
address at which it can receive SNMP messages. The advertisements also contain time-to-live, or
holdtime information, which is the length of time a re ceiving device holds CDP information before
discarding it. Each device also listens to the messages sent by other devices to learn about neighb oring
devices.
On the switch, CDP enables Network Assistant to display a graphi cal view of the network. The switch
uses CDP to find cluster candidates and maintain information about cluster members and other devices
up to three cluster-enabled devices away from the command switch by default.