Users Guide

Figure 20. 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 14. 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 21. LLDPDU Frame
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Link Layer Discovery Protocol (LLDP)