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Link Layer Discovery Protocol (LLDP)
Link Layer Discovery Protocol (LLDP) — dened by IEEE 802.1AB — is a protocol that enables a local area network (LAN) device to
advertise its conguration and receive conguration information from adjacent LLDP-enabled LAN infrastructure devices.
802.1AB (LLDP) Overview
The collected information is stored in a management information base (MIB) on each device, and is accessible via simple network
management protocol (SNMP).
Protocol Data Units
Conguration information is exchanged in the form of Type, Length, Value (TLV) segments.
• Type — The information included in the TLV.
• Length — The value, in octets, of the TLV after the Length eld.
• Value — The conguration information that the agent is advertising.
The chassis ID TLV is shown in the following illustration.
Figure 75. Type, Length, Value (TLV) Segment
TLVs are encapsulated in a frame called an LLDP data unit (LLDPDU) (shown in the following table), which is transmitted from one LLDP-
enabled device to its LLDP-enabled neighbors. LLDP is a one-way protocol. LLDP-enabled devices (LLDP agents) can transmit and/or
receive advertisements, but they cannot solicit and do not respond to advertisements.
There are ve types of TLVs. All types are mandatory in the construction of an LLDPDU except Optional TLVs. You can congure the
inclusion of individual Optional TLVs.
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