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In a heterogeneous network, it is important that different types of network devices from different vendors 
can discover one other and exchange configuration for interoperability and management sake. This 
calls for a standard configuration exchange platform.  
To address the needs, the IETF drafted the Link Layer Discovery Protocol (LLDP) in IEEE 802.1AB. The 
protocol operates on the data link layer to exchange device information between directly connected 
devices. With LLDP, a device sends local device information as TLV (type, length, and value) triplets in 
LLDPDUs to the directly connected devices, and at the same time, stores the device information 
received in LLDPDUs sent from the LLDP neighbors in a standard management information base (MIB). 
It allows a network management system to fast detect Layer-2 network topology change and identify 
what the change is.  

LLDP sends device information in LLDP data units (LLDPDUs). LLDPDUs are encapsulated in Ethernet 
II or SNAP frames. 
1)  LLDPDUs encapsulated in Ethernet II 

LLDPDU encapsulated in Ethernet II 

 

 

 
The fields in the frame are described in 

:  

Description of the fields in an Ethernet II encapsulated LLDPDU 

Destination MAC address  The MAC address to which the LLDPDU is advertised. It is fixed to 

0x0180-C200-000E, a multicast MAC address.