SNR S2940-8G-v2 Switch Configuration Guide
LLDP Function Operation Configuration
Chapter 7
LLDP Function Operation Configuration
7.1 Introduction to LLDP Function
Link Layer Discovery Protocol (LLDP) is a new protocol defined in 802.1ab. It enables neighbor
devices to send notices of their own state to other devices, and enables all ports of every device
to store information about them. If necessary, the ports can also send update information to the
neighbor devices directly connected to them, and those neighbor devices will store the information
in standard SNMP MIBs. The network management system can check the layer-two connection
state from MIB. LLDP won't configure or control network elements or flows, but only report the
configuration of layer-two. Another content of 802.1ab is to utilizing the information provided by
LLDP to find the conflicts in layer-two. IEEE now uses the existing physical topology, interfaces
and Entity MIBs of IETF.
To simplify, LLDP is a neighbor discovery protocol. It defines a standard method for Ethernet
devices, such as switches, routers and WLAN access points, to enable them to notify their exis-
tence to other nodes in the network and store the discovery information of all neighbor devices.
For example, the detail information of the device configuration and discovery can both use this
protocol to advertise.
In specific, LLDP defines a general advertisement information set, a transportation advertise-
ment protocol and a method to store the received advertisement information. The device to ad-
vertise its own information can put multiple pieces of advertisement information in one LAN data
packet to transport. The type of transportation is the type length value (TLV) field. All devices sup-
porting LLDP have to support device ID and port ID advertisement, but it is assumed that, most
devices should also support system name, system description and system performance advertise-
ment. System name and system description advertisement can also provide useful information
for collecting network flow data. System description advertisement can include data such as the
full name of the advertising device, hardware type of system, the version information of software
operation system and so on.
802.1AB Link Layer Discovery Protocol will make searching the problems in an enterprise
network an easier process and can strengthen the ability of network management tools to discover
and maintain accurate network topology structure.
Many kinds of network management software use Automated Discovery function to trace the
change and condition of topology, but most of them can reach layer-three and classify the devices
into all IP subnets at best. This kind of data are very primitive, only referring to basic events like
the adding and removing of relative devices instead of details about where and how these devices
operate with the network.
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