CHAPTER
17-1
Cisco Systems IntelligentGigabit Ethernet Switch Modules for the IBM BladeCenter, Software Configuration Guide
24R9746
17
Configuring CDP
This chapter describes how to configure Cisco Discovery Protocol (CDP) on your Cisco Syste ms
Intelligent Gigabit Ethernet Switch Module.
Note For complete syntax and usage information for the commands used in this chapter, see the command
reference for this release and the Cisco IOS Configuration Fundamentals Command Reference for Cisco
IOS Release12.1.
This chapter consists of these sections:
•Understanding CDP, page 17-1
•Configuring CDP, page 17-2
•Monitoring and Maintaining CDP, page 17-5

Understanding 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.
The switch supports CDP Version 2.