Name: Cisco 4500M
Brand: Cisco
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CHAPTER

20-1

Software Configuration Guide—Release 12.2(25)EW

OL-6696-01

Understanding and Configuring CDP

This chapter describes how to configure Cisco Discovery Protocol (CDP) on the Catalyst 4500 series

switch. It also provides guidelines, procedures, and configuration examples.

This chapter includes the following major sections:

• Overview of CDP, page 20-1

• Configuring CDP, page 20-2

Note For complete syntax and usage information for the commands used in this chapter, refer to the

Cisco IOS Configuration Fundamentals Configuration Guide, Release 12.2;

Cisco IOS System Management; Configuring Cisco Discovery Protocol (CDP) at this URL:

http://www.cisco.com/univercd/cc/td/doc/product/software/ios122/122cgcr/fun_c/fcprt3/fcd301c.htm

and to the Cisco IOS Configuration Fundamentals Command Reference, Release 12.1;

Cisco IOS System Management Commands; and CDP Commands publication at this URL:

http://www.cisco.com/univercd/cc/td/doc/product/software/ios122/122cgcr/fun_r/frprt3/frd3001b.htm

Note For complete syntax and usage information for the switch commands used in this chapter, refer to the

Catalyst 4500 Series Switch Cisco IOS Command Reference and related publications at

http://www.cisco.com/univercd/cc/td/doc/product/software/ios122/122cgcr/index.htm.

Overview of CDP

CDP is a protocol that runs over Layer 2 (the data link layer) on all Cisco routers, bridges, access servers,

and switches. CDP allows network management applications to discover Cisco devices that are

neighbors of already known devices, in particular, neighbors running lower-layer, transparent

protocols.With CDP, network management applications can learn the device type and the SNMP agent

address of neighboring devices. CDP enables applications to send SNMP queries to neighboring devices.

CDP runs on all LAN and WAN media that support Subnetwork Access Protocol (SNAP).

Each CDP-configured device sends periodic messages to a multicast address. Each device advertises at

least one address at which it can receive SNMP messages. The advertisements also contain the

time-to-live, or holdtime information, which indicates the length of time a receiving device should hold

CDP information before discarding it.

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