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Configuring CDP
This chapter describes how to configure the Cisco Discovery Protocol (CDP) on the Catalyst enterprise
LAN switches.
Note
For complete syntax and usage information for the commands that are used in this chapter, refer to the
Catalyst 4500 Series, Catalyst 2948G, Catalyst 2948G-GE-TX, and Catalyst 2980G Switches Command
Reference.
This chapter consists of these sections:
•
•
•
Understanding How CDP Works
CDP is a media- and protocol-independent protocol that runs on all 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
native VLAN and port duplex mismatches.
Network management applications can retrieve the device type and SNMP-agent address of neighboring
Cisco devices using CDP. This feature allows applications to send SNMP queries to neighboring devices.
CDP allows network management applications to discover Cisco devices that are neighbors of already
known devices, in particular, neighbors running lower-layer, transparent protocols.
CDP runs on all media that support Subnetwork Access Protocol (SNAP). CDP runs over the data link
layer only.
Cisco devices do not forward CDP packets. When new CDP information is received, old information is
discarded.
Default CDP Configuration
Table 21-1
Catalyst 4500 Series, Catalyst 2948G, Catalyst 2948G-GE-TX, and Catalyst 2980G Switches Software Configuration Guide—Release 8.2GLX
78-15908-01
Understanding How CDP Works, page 21-1
Default CDP Configuration, page 21-1
Configuring CDP on the Switch, page 21-2
shows the default CDP configuration.
C H A P T E R
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21-1
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Troubleshooting
