What is Cisco Discovery Protocol?
The Cisco Discovery Protocol (CDP) is the proprietary Cisco Data Link Layer protocol of the OSI model. It is used with most Cisco network 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 to operate on different network layer protocols to learn from each other.
In February 2006, Hewlett-Packard removed support for CDP information transfer from its products. CDP support has also been replaced by the IEEE 802.1AB Link Layer Discovery Protocol, a CDP-like standard implemented by many vendors.
CDP shares several types of information called announcements. In addition to the version of the operating system and all IP addresses of each protocol configured on the port that the CDP frame (data) is sent to, CDP shares the following information:
- host name
- Origin Information Port ID
- Native virtual local area network (VLAN)
- Every device type and model
- Duplex settings
- VLAN trunking protocol domain, a proprietary Cisco Layer 2 messaging protocol
- The force that is pulled
- Other data on specific devices
Details of this information can be expanded using the data length format data frame format, also referred to as the data packet format.