Cisco Discovery Protocol
CDP is media- and protocol-independent and runs on all Cisco-manufactured
equipment, including routers, bridges, access and communications servers, and
switches. CDP allows network management applications to dynamically discover Cisco
devices that are neighbors of already-known devices, in particular, neighbors
running lower-layer, transparent protocols. CDP runs on all media that support
Subnetwork Access Protocol (SNAP). CDP also runs over the data link layer only,
not the network layer. Cisco devices do not forward CDP packets.