Cisco Discovery Protocol

Cisco Systems in 1994^[1] by Keith McCloghrie and Dino Farinacci. It is used to share information about other directly connected Cisco equipment, such as the operating system version and IP address. CDP can also be used for On-Demand Routing, which is a method of including routing information in CDP announcements so that dynamic routing protocols

Virtual Local Area Network (VLAN) Trunking Protocol (VTP). By default, CDP announcements are sent every 60 seconds on interfaces that support Subnetwork Access Protocol (SNAP) headers, including Ethernet, Frame Relay and Asynchronous Transfer Mode (ATM). Each Cisco device that supports CDP stores the information received from other devices in a table that can be viewed using the show cdp neighbors command. This table is also accessible via Simple Network Management Protocol (SNMP). The CDP table information is refreshed each time an announcement is received, and the hold time for that entry is reinitialized. The hold time specifies the lifetime of an entry in the table - if no announcements are received from a device for a period in excess of the hold time, the device information is discarded (default 180 seconds).^{[citation needed}

IEEE standard that is implemented by multiple vendors and is functionally similar to CDP.^[2]