What is LLDP (Link Layer Discovery Protocol) used for?

• A. A protocol for encrypting data on a link layer.
• B. Link Layer Discovery Protocol advertising device/port info to neighbors.
• C. A tool that measures latency and packet loss across routes.
• D. A protocol used to synchronize clocks between devices.

Answer: (B)

LLDP is used to discover neighboring devices at the data link layer by exchanging information about each device and its ports. It works by sending LLDP data units that carry TLVs such as chassis ID (the device), port ID, system name, system description, capabilities, and management address, enabling both devices to learn who is directly connected to them. This vendor-neutral protocol helps network management systems map the local topology, verify connections, and assist with inventory, troubleshooting, and automated configuration across mixed vendors. It is not designed for encrypting data, measuring latency or packet loss, or clock synchronization (roles filled by encryption protocols, performance tools, or time-sync protocols, respectively).