Simple definition
Cisco Discovery Protocol (CDP) is a Cisco proprietary Layer 2 protocol that lets compatible network devices advertise information to directly connected neighbours.
Technical definition
CDP advertisements can contain a device name, platform, software information, capabilities and the local port identifier. CDP operates between directly connected devices and should be controlled on untrusted interfaces.
What is CDP used for?
Identify neighbouring switches, routers and phones, and help document physical network connections.
Practical example
On a Cisco switch, the command show cdp neighbors detail displays information about directly connected devices.
Common problems
- Owner Protocol
- Exhibit of information
- CDP disabled on some ports
Related terms
To be noted: precise behaviors and commands may vary depending on the versions, products and architectures.