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Figure 66. Type, Length, Value (TLV) Segment
TLVs are encapsulated in a frame called an LLDP data unit (LLDPDU), 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 five types of TLVs (as shown in the below table). All types are mandatory in the construction of an LLDPDU except
Optional TLVs. You can configure the inclusion of individual Optional TLVs.
Table 37. Type, Length, Value (TLV) Types
Type TLV Description
0
End of LLDPDU Marks the end of an LLDPDU.
1
Chassis ID The Chassis ID TLV is a mandatory TLV that identifies the chassis containing the
IEEE 802 LAN station associated with the transmitting LLDP agent.
2
Port ID The Port ID TLV is a mandatory TLV that identifies the port component of the
MSAP identifier associated with the transmitting LLDP agent.
3
Time to Live The Time To Live TLV indicates the number of seconds that the recipient LLDP
agent considers the information associated with this MSAP identifier to be valid.
Optional Includes sub-types of TLVs that advertise specific configuration information.
These sub-types are Management TLVs, IEEE 802.1, IEEE 802.3, and TIA-1057
Organizationally Specific TLVs.
Figure 67. LLDPDU Frame
Configure LLDP
Configuring LLDP is a two-step process.
1. Enable LLDP globally.
2. Advertise TLVs out of an interface.
Link Layer Discovery Protocol (LLDP)
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