CDP Command List

The Cisco Discovery Protocol (CDP) is a protocol that Cisco devices use to learn and share information about each other. Cisco devices, such as routers and switches, can discover neighboring Cisco devices through CDP.

  • By default, CDP is enabled on all interfaces.
  • CDP only shares information with directly connected (neighboring) devices.
  • CDP works when there is a valid Data Link layer connection.
  • CDP works regardless of the Network layer and other protocols used. It can discover information on LANs, Frame Relay, and other network architectures.

Use the following commands to customize and view CDP information.

Use . . .

To . . .

 
Router(config)#cdp holdtime <10-255>

Specify the amount of time that information in a packet is still valid (default = 180 seconds)
Use the no cdp holdtime command to reset the value to its default.

 
Router(config)#cdp timer <5-900>

Specify how often CDP packets are exchanged (default = 60 seconds)
Use the no cdp timer command to reset the value to its default.

 
Router(config)#cdp run

Enable CDP on the router

 
Router(config)#no cdp run

Disable CDP on a router, to prevent the router from exchanging CDP packets

 
Router(config-if)#cdp enable

Turns CDP for an interface on

 
Router(config-if)#no cdp enable

Turns CDP for an interface off

 
Router#show cdp

View CDP information

 
Router#show cdp interface

Show information about neighbors accessed through an interface
Show CDP configuration information for the router including the holdtime, encapsulation, and CDP exchange interval

 
 
Router#show cdp neighbors

Show information about all neighboring Cisco devices including:

  • Device ID
  • Local interface
  • Holdtime
  • Capability
  • Platform
  • Port ID 
Router#show cdp neighbors detail

Shows all information for the show cdp neighbors command and adds:

  • Network address (such as the IP address)
  • Enabled protocols
  • Software version 
Router#show cdp entry *

Show the same information as show cdp neighbors detail

 
Router#show cdp entry <name of the neighbor>

Show the same information as show cdp neighbors detail, but only for the named neighbor

 
Router#show cdp traffic

Show the number of CDP advertisements sent and received

Examples
The following commands turn on CDP for the router and configures it to send CDP packets every 90 seconds.

Router(config)#cdp run
Router(config)#cdp timer 90

The following commands turn off CDP on the router's first Ethernet interface.

Router(config)#int eth 0
Router(config-if)#no cdp enable



Credit: Testout 640-802 CCNA Notes