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Link Layer Discovery Protocol (LLDP)
This chapter describes how to congure and use the link layer discovery protocol (LLDP).
802.1AB (LLDP) Overview
LLDP — dened by IEEE 802.1AB — is a protocol that enables a local area network (LAN) device to advertise its conguration and receive
conguration information from adjacent LLDP-enabled LAN infrastructure devices.
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
Conguration information is exchanged in the form of Type, Length, Value (TLV) segments.
Type — The kind of information included in the TLV.
Length — The value, in octets, of the TLV after the Length eld.
Value — The conguration information that the agent is advertising.
The chassis ID TLV is shown in the following illustration.
Figure 74. 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 congure the
inclusion of individual Optional TLVs.
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