CDP for discovering and viewing simple configuration information of the neighboring Cisco devices, you can start working CDP does not require IP or other layer 3 protocol
CDP has two timers that update timer and keep the timer , by default, is the former 60s, the latter 180s
Works:
Cisco equipment every 60s, CDP sent from the interface enabled out a CDP information, neighboring Cisco devices after receiving this information, update their CDP neighbor table; neighbor table in CDP Cisco device, just CDP entries received update information holding timer is set to 180s, at the same time start the countdown, when the countdown from 0s to 180s does not receive the device during hair entry corresponding to the update information, the system will equipment entry is deleted from the CDP neighbor table
command:cdp run <br/>// 在config下开启cdp，但一般是默认开启的，可以通过no cdp run 关闭，可以节省带宽
