Cisco Discovery Protocol

What Does Cisco Discovery Protocol Mean?

Cisco Discovery Protocol (CDP) is Cisco’s proprietary, data link layer protocol of the OSI model. It is used with most Cisco networking equipment, including routers, bridges, access servers and switches. CDP shares information about connected network devices such as interfaces used by routers, IP addresses and the operating system version. CDP can also allow two systems that are operating on different network layer protocols to learn about each other.


In February 2006, Hewlett-Packard removed support for transmitting CDP information from their products. CDP support has also been replaced with IEEE 802.1AB Link Layer Discovery Protocol, a standard similar to CDP and implemented by numerous vendors.

Techopedia Explains Cisco Discovery Protocol

CDP shares different kinds of information called announcements. In addition to the version of the OS and all IP addresses from every protocol that are configured on the port where the CDP frame (data) is sent, CDP shares the following information:

  • Host name
  • Originating information port identifier
  • Native virtual local area network (VLAN)
  • Each device type and model
  • Duplex settings
  • VLAN Trunking Protocol domain, a proprietary Cisco Layer 2 messaging protocol
  • The power drawn
  • Other data regarding specific devices

Details of this information can be expanded with the use of the type-length-value data frame format, which is also called data packet format.


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Margaret is an award-winning technical writer and teacher known for her ability to explain complex technical subjects to a non-technical business audience. Over the past twenty years, her IT definitions have been published by Que in an encyclopedia of technology terms and cited in articles by the New York Times, Time Magazine, USA Today, ZDNet, PC Magazine, and Discovery Magazine. She joined Techopedia in 2011. Margaret's idea of a fun day is helping IT and business professionals learn to speak each other’s highly specialized languages.