Administrator Guide

Link Layer Discovery Protocol (LLDP)

802.1AB (LLDP) 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 simple network

management protocol (SNMP).

Protocol Data Units

Configuration 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 67. Type, Length, Value (TLV) Segment

TLVs 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/or

receive 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 the

inclusion of individual Optional TLVs.

Table 35. Type, Length, Value (TLV) Types

Type TLV Description

0 End of LLDPDU Marks the end of a LLDPDU.

1 Chassis ID An administratively assigned name that

identifies the LLDP agent.

2 Port ID An administratively assigned name that

identifies a port through which TLVs are

sent and received.

3 Time to Live An administratively assigned name that

identifies a port through which TLVs are

sent and received.

420 Link Layer Discovery Protocol (LLDP)