Link Layer Discovery Protocol (LLDP)This chapter describes how to configure and use the link layer discovery protocol (LLDP).802.1AB (LLDP) OverviewLLDP — defined by IEEE 802.1AB — is a protocol that enables a local area network (LAN) device to advertise its configuration and receiveconfiguration 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 networkmanagement protocol (SNMP).Protocol Data UnitsConfiguration 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 field.• Value — The configuration information that the agent is advertising.The chassis ID TLV is shown in the following illustration.Figure 73. Type, Length, Value (TLV) SegmentTLVs 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/orreceive advertisements, but they cannot solicit and do not respond to advertisements.There are five types of TLVs. All types are mandatory in the construction of an LLDPDU except Optional TLVs. You can configure theinclusion of individual Optional TLVs.26Link Layer Discovery Protocol (LLDP) 493
