What is Cisco Discovery Protocol in Cisco Routers?

CDP or Cisco Discovery Protocol is a protocol owned by Cisco and integrated in all Cisco devices including Cisco routers. It employs a Layer 2 protocol and is used to track the availability of nearby Cisco devices. It can collect, learn, and share details and data on other Cisco systems directly. The collected information contains IP addresses, hardware platforms and operating systems.

The CDP is employed to assist network layer protocols to familiarize with one another and gauge the configuration of such connected devices. Cisco routers, by default, come enabled with this system and send and receives messages about condition of other devices.

The device and the operating system version make the information of each message differ from each other. Other than information on IP and hardware platform, the message may include details on duplex settings, hostname, and the active interfaces on Cisco systems. The received messages are stored by Cisco routers in a table form which is updated every time a new message arrives.

ESXi administrators can find out which Cisco port is employed with a particular vSwitch from the Cisco Discovery Protocols in the VMware. Properties of a Cisco switch like device ID and software version is displayed to administrators when the vSwitch gets connected to a protocol.

The new updated version 2 of Cisco Discovery Protocol can transfer native VLAN information between Cisco switches. This feature was unavailable in the version 1. The console shows an error notification if there is mismatch of native VLAN. To use CDP, interfaces should be compatible with Subnet Access Protocol headers.