Cisco Discovery Protocol (CDP) is a layer two protocol used by Cisco devices to automate network discovery. Cisco IOS commands such as show cdp neighbors and show cdp neighbors detail provide information such as device type, model number, IOS version and IP addressing. Given a console or virtual terminal session on one Cisco device, CDP information is available to that device about all other Cisco devices on attached network segments.
From a security standpoint, CDP functionality needs to be limited to a trusted local network only. CDP information should never leak onto the global Internet.
The scope of CDP is limited to Cisco devices only. CDP does not support network discovery or management for multivendor deployments.