Cisco Discovery Protocol

Cisco Discovery Protocol in short CDP is a propritery protocol used to findout what all devices are connected to a particular router or switch. Some of the main commands that could be used on routers are as follows:

# show cdp neighbor  This command displays all the devices connected to the said router. The devices are recognised as follows :

T - Trans Bridge   S - Switch   R - Router   
r - Repeater    B - Source Route Bridge    I - IGRP    H - Host

Two other commands which give the same result but in a more detailed fashion are :

# show cdp neighbors detail    is the same as    # show cdp entry *

Gathering Interface Traffic Information

# show cdp traffic

Gathering Port and Interface Information

# show cdp interface

Disabling CDP on a router

# no cdp run

Disable CDP on a per interface basis

(config-if)# no cdp enable
It is    cdp enable    by default.