Link Layer Discovery Protocol (Lldp); Overview; Protocol Data Units - Dell PowerEdge M IO Aggregator Command Reference Manual

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.
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)
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.
TLV Header
TLV Type TLV Length
Value
(1-127)
9 bits
7 bits 0-511 octets
Chassis ID Sub-type
1 octet
Chassis ID
fnC0057mp
1- 255 octets
(Figure
Link Layer Discovery Protocol (LLDP) | 167
14
Figure 14-1
14-2), which is transmitted