Cisco Discovery Protocol

A

Cisco Discovery Protocol (CDP) is a Cisco proprietary protocol used to share information about directly connected Cisco equipment, such as routers, switches, and firewalls.

A) It is a Cisco-proprietary protocol: This statement is true. Cisco Discovery Protocol is a proprietary protocol developed by Cisco Systems, which means it can only be used with Cisco networking devices.

B) It runs on the network layer: This statement is false. CDP operates at the data link layer of the OSI model. Specifically, it runs on top of the Media Access Control (MAC) layer, which is layer 2 of the OSI model.

C) It can discover information from routers, firewalls, and switches: This statement is true. CDP can discover information about directly connected Cisco networking devices, including the device's IP address, device type, and the platform on which the device is running.

D) It runs on the physical layer and the data link layer: This statement is false. CDP only operates at the data link layer and not on the physical layer. The physical layer is responsible for transmitting raw bits over a physical medium, such as copper or fiber optic cables, whereas CDP operates on top of the data link layer to provide information about directly connected networking devices.

In summary, Cisco Discovery Protocol is a proprietary protocol developed by Cisco Systems that operates at the data link layer. It allows for the discovery of information about directly connected Cisco networking devices and cannot run on the physical layer.