Cisco Discovery Protocol

D

Cisco Discovery Protocol (CDP) is a proprietary protocol developed by Cisco Systems that is used to share information about directly connected devices, such as routers, switches, and gateways.

The correct answer to the question is A. It discovers the routers, switches and gateways.

CDP operates at the data link layer of the OSI model (layer 2), which means it is responsible for the transmission of data packets between adjacent network devices. Specifically, CDP runs over the Media Access Control (MAC) layer protocol and is therefore classified as a Layer 2 protocol.

CDP works by sending out periodic messages, known as advertisements, to other devices on the same network segment. These messages contain information about the sending device, such as its hostname, IP address, and the interface through which it is connected.

In addition, CDP can also provide information about the capabilities of the device, such as the version of IOS running on a Cisco router or the type of hardware installed in a Cisco switch. This information can be used by network administrators to identify and troubleshoot network issues.

CDP is a Cisco proprietary protocol, meaning it is only supported on Cisco devices. However, some other vendors offer similar protocols, such as Link Layer Discovery Protocol (LLDP), which is an industry-standard protocol. LLDP provides similar functionality to CDP and is supported by a variety of network devices from different vendors.

In summary, Cisco Discovery Protocol is a Layer 2 protocol that is used to discover directly connected Cisco devices and exchange information about their configuration and capabilities.