Cisco Discovery Protocol

CDP is an information-gathering tool that is used by Cisco routers and switches to ascertain basic information (summary of protocols and addresses) about neighboring routers and switches.

Following are the features of CDP:

1. CDP runs over data link layer (layer 2) –it connects physical media to the upper-layer protocol.
2. Ascertain addresses for SNMP (Application Layer) management.
3. Ascertain addresses of other devices to log in to them.
4. Support forwarding CDP message over an interface. -Interface must support SNMP header.
5. All LAN interfaces (FR, HDLC, ATM) support CDP.
6. CDP discovers the following:

                                                              i.            Device identifier

                                                            ii.            Address list

                                                          iii.            Port identifier

                                                          iv.            Capabilities list

                                                            v.            Platform-model &OS

CDP Command Summary

1.CDP is enabled by default

2.To disable CDP for the entire device

    Router(config)#no cdp run

3.To re-enable CDP for the entire device

   Router(config)# cdp run

4.To disable CDP on an interface

  Router(config-if)#no cdp enable

5. To re-enable CDP on an interface

  Router(config-if)# cdp enable

6.To display CDP information about neighboring devices

   Router#show cdp neighbor

7.To display detailed CDP information about neighboring devices

   Router#show cdp neighbor details

   Or

   Router#show cdp entry *

8.To display traffic on an interface

  Router#sh cdp traffic

9.To display configuration information and interface for a device

  Router#show cdp interface