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Link Layer Discovery Protocol (LLDP)
32.1
LLDP Overview
The LLDP (Link Layer Discovery Protocol) is a layer 2 protocol. It allows a network device to
advertise its identity and capabilities on the local network. It also allows the device to maintain and
store information from adjacent devices which are directly connected to the network device. This
helps an administrator discover network changes and perform necessary network reconfiguration
and management. The device information is encapsulated in the LLDPDUs (LLDP data units) in the
form of TLV (Type, Length, Value). Device information carried in the received LLDPDUs is stored in
the standard MIB.
The Switch supports these basic management TLVs.
•
End of LLDPDU (mandatory)
•
Chassis ID (mandatory)
•
Port ID (mandatory)
•
Time to Live (mandatory)
•
Port Description (optional)
•
System Name (optional)
•
System Description (optional)
•
System Capabilities (optional)
•
Management Address (optional)
The Switch also supports the IEEE 802.1 and IEEE 802.3 organizationally-specific TLVs.
IEEE 802.1 specific TLVs:
•
Port VLAN ID TLV (optional)
•
Port and Protocol VLAN ID TLV (optional)
IEEE 802.3 specific TLVs:
•
MAC/PHY Configuration/Status TLV (optional)
•
Power via MDI TLV (optional, For PoE models only)
•
Link Aggregation TLV (optional)
•
Maximum Frame Size TLV (optional)
The optional TLVs are inserted between the Time To Live TLV and the End of LLDPDU TLV.
The next figure demonstrates that the network devices Switches and Routers (S and R) transmit
and receive device information via LLDPDU and the network manager can query the information
using Simple Network Management Protocol (SNMP).
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