Chapter 20 Configuring Cdp; Understanding Cdp; Configuring Cdp - Cisco 3845 - Security Bundle Router Software Manual

Configuring CDP

This chapter describes how to configure Cisco Discovery Protocol (CDP) on the Cisco ME 3800X and
ME 3600X switch.
For complete syntax and usage information for the commands used in this chapter, see the command
Note
reference for this release and the "System Management Commands" section in the Cisco IOS
Configuration Fundamentals Command Reference, Release 12.2.
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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 Management 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 CDP 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 receiving device holds CDP information before
discarding it. Each device also listens to the messages sent by other devices to learn about neighboring
devices.
The switch supports CDP Version 2.
OL-23400-01
Understanding CDP, page 20-1
Configuring CDP, page 20-2
Monitoring and Maintaining CDP, page 20-5
C H A P T E R
Cisco ME 3800X and 3600X Switch Software Configuration Guide
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