How to use Cisco Discovery Protocol

Last updated: 25-01-2026

Cisco Discovery Protocol (CDP)

Cisco Discovery Protocol (CDP) is a Cisco proprietary Layer 2 protocol used to discover information about directly connected Cisco devices. This includes the device's hostname, hardware type, software version, and IP address. CDP is a passive protocol, meaning it does not require any configuration on neighboring devices.

CDP is used for a variety of purposes, including:

  • Network inventory: Create a map of the network and identify all connected devices.
  • Troubleshooting: Identify devices connected to a particular interface or determine the path between two devices.
  • Security: Identify unknown devices on the network.

Enabling and Using CDP

To enable CDP on a Cisco device, use the following command:

cdp run

To view information about directly connected devices, use:

show cdp neighbors

CDP Diagram

CDP Diagram

Benefits of Cisco CDP

  • Simple and easy-to-use protocol.
  • Widely supported by Cisco devices.
  • No configuration required on neighboring devices.
  • Can gather a variety of information about directly connected devices.

Limitations of Cisco CDP

  • Layer 2 protocol: Cannot discover devices that are not directly connected.
  • Informational only: Cannot control devices on the network.
  • Security risk: Can be exploited if not configured properly.

Conclusion

Cisco CDP is a valuable and widely supported tool for network administrators and engineers. It helps quickly gather information about connected devices for troubleshooting, planning network changes, and improving security. However, be mindful of its limitations and configure it carefully to avoid potential security risks.