225Configuring LLDPOverviewBackgroundIn a heterogeneous network, a standard configuration exchange platform ensures that different types ofnetwork devices from different vendors can discover one another and exchange configuration for thesake of interoperability and management.The IETF drafted the Link Layer Discovery Protocol (LLDP) in IEEE 802.1AB. The protocol operates on thedata link layer to exchange device information between directly connected devices. With LLDP, a devicesends local device information (including its major functions, management IP address, device ID, andport ID) as TLV (type, length, and value) triplets in LLDP Data Units (LLDPDUs) to the directly connecteddevices. At the same time, the device stores the device information received in LLDPDUs sent from theLLDP neighbors in a standard management information base (MIB). For more information about MIBs,see Network Management and Monitoring Configuration Guide. LLDP enables a network managementsystem to quickly detect and identify Layer 2 network topology changes.Basic conceptsLLDPDU formatsLLDP sends device information in LLDPDUs. LLDPDUs are encapsulated in Ethernet II or SubnetworkAccess Protocol (SNAP) frames.1. Ethernet II-encapsulated LLDPDU formatFigure 76 Ethernet II-encapsulated LLDPDU formatTable 21 Fields in an Ethernet II-encapsulated LLDPDUField DescriptionDestination MAC address MAC address to which the LLDPDU is advertised. It is fixed to0x0180-C200-000E, a multicast MAC address.
