Configuring Cdp; Understanding How Cdp Works - Cisco WS-C6506 Software Manual

Configuring CDP

This chapter describes how to configure the Cisco Discovery Protocol (CDP) on the Catalyst 6500 series
switches.
For complete syntax and usage information for the commands that are used in this chapter, refer to the
Note
Catalyst 6500 Series Switch Command Reference publication.
This chapter consists of these sections:
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Understanding How CDP Works

CDP was enhanced in software release 8.1(1) to facilitate the backward compatibility with the newer,
higher-powered Cisco IP phones. With this enhanced CDP, a Cisco IP phone can negotiate its power
requirements to the switch within the CDP packet. The switch uses this information to ensure that it does
not oversubscribe the available power.
CDP is a media- and protocol-independent protocol that runs on all the Cisco-manufactured equipment
including routers, bridges, access and communication servers, and switches. Using CDP, you can view
information about all the Cisco devices that are directly attached to the switch. In addition, CDP detects
the native VLAN and port duplex mismatches.
The network management applications can retrieve the device type and SNMP-agent address of the
neighboring Cisco devices using CDP. This feature enables the applications to send the SNMP queries
to the neighboring devices. CDP allows the network management applications to discover the Cisco
devices that are the neighbors of the already known devices, in particular, the neighbors running the
lower-layer, transparent protocols.
CDP runs on all media that support Subnetwork Access Protocol (SNAP). CDP runs over the data link
layer only.
The Cisco devices never forward the CDP packets. When new CDP information is received, the Cisco
devices discard old information.
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Understanding How CDP Works, page 31-1
Default CDP Configuration, page 31-2
Configuring CDP on the Switch, page 31-2
C H A P T E R
Catalyst 6500 Series Switch Software Configuration Guide—Release 8.7
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