Reference Guide

Link Layer Discovery Protocol (LLDP) | 167
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Link Layer Discovery Protocol (LLDP)
An Aggregator auto-configures to support the link layer discovery protocol (LLDP) for the auto-discovery
of network devices. You can use CLI commands to display acquired LLDP information, clear LLDP
counters, and debug LACP operation.
Overview
LLDP—defined by IEEE 802.1AB—is a protocol that enables a local area network (LAN) device to
advertise its configuration and receive configuration 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 a simple network management protocol (SNMP).
Protocol Data Units
Configuration information is exchanged in the form of type, length, value (TLV) segments. Figure 14-1
shows the Chassis ID TLV.
• Type—Indicates the type of field that a part of the message represents.
• Length—Indicates the size of the value field (in bytes).
• Value—Indicates the data for this part of the message.
Figure 14-1. Type, Length, Value (TLV) Segment
TLVs are encapsulated in a frame called an LLDP data unit (LLDPDU) (Figure 14-2), 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.
Chassis ID Sub-type
fnC0057m
p
Chassis ID
7 bits
9 bits
1 octet
1- 255 octets
TLV Type
(1-127)
TLV Length
Value
TLV Header
0-511 octets