The Link Layer Discovery Protocol (LLDP) is a neighbor discovery protocol used by network devices to advertise their identity, capabilities, and interconnections on an IEEE 802 LAN network. LLDP is vendor-neutral. The protocol defines a standard way for Ethernet devices to advertise information about themselves to their network neighbors, and store the information they discover from other devices.

LLDP operates above the MAC service layer and can be used in any networking device that implements a MAC service. Information gathered with LLDP is stored in the device in a standard management information database (MIB) and can be queried with the Simple Network Management Protocol (SNMP). For example, a LAN switch and a router advertise chassis/port IDs and system descriptions to each other. The devices store the information they learn about each other in local MIB databases accessible through SNMP. The network management system retrieves the data stored by each device and builds a network topology map.