What protocol allows Cisco devices to discover each other on the same LAN?

The correct choice is CDP (Cisco Discovery Protocol) because this protocol is specifically designed for Cisco devices to communicate their identities and attributes to each other on the same local area network (LAN). CDP allows devices to share information such as device names, IP addresses, and capabilities, which is essential for network management and device discovery.

Since CDP is a proprietary protocol used exclusively by Cisco devices, it enhances network visibility and simplifies troubleshooting and configuration tasks performed by network engineers. It facilitates automated discovery, allowing for easier management in environments with numerous Cisco devices.

Other protocols listed, such as TCP and UDP, serve general transport layer functions for data communication but do not provide discovery mechanisms for devices on the network. IP, being a network layer protocol, is responsible for addressing and routing packets, but it doesn’t facilitate the discovery of devices on a LAN in the way that CDP does.