The Cisco Discovery Protocol (CDP) is basically used to obtain protocol addresses of adjacent devices and platforms that discover these devices. CDP can also provide associated interface information for the use of routers. CDP is a stand-alone media protocol that runs on all Cisco itself manufactured, including routers, bridges, access servers, and switches.
In conjunction with the CDP management information base MIB, the network management application can enable the network management app to know the device type and the SNMP proxy address of adjacent devices, and send SNMP query requests to these devices. The Cisco discovery protocol supports Cisco-CDP-MIB.
CDP runs on all media to support subnet access protocol SNAP, including LAN, frame relay, and asynchronous transmission mode ATM physical media. The CDP is only running on the data link layer, so two systems supporting different network layer protocols have been familiar with each other.
Each device configured by the CDP sends periodic information, such as what we know to the multicast address. At least one address per device, under this address, it can receive SNMP information. Advertising includes information such as survival, or holding time, which points out the length of time for receiving the device to keep the CDP information before canceling. In addition, each device also pays attention to the periodic CDP information issued by other devices, from which neighboring device information and determine when the media interfaces of those devices grow or decrease.
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