SNR S2989G-48TX-POE — понимание LLDP: Протокол для обнаружения соседей в сети [82/553]

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2-18

S2989G-24TX Operation Manual Chapter 2 Layer 2 services

Configuration

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 existence 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

advertisement protocol and a method to store the received advertisement information.

The device to advertise 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 supporting 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 advertisement. 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.

Layer 2 discovery covers information like which devices have which ports, which

switches connect to other devices and so on, it can also display the routs between clients,

switches, routers, application servers and network servers. Such details will be very

meaningful for schedule and investigate the source of network failure.

LLDP will be a very useful management tool, providing accurate information about

network mirroring, flow data and searching network problems.

2.5.2

LLDP Function Configuration Task Sequence

1. Globally enable LLDP function

2. Configure the port-based LLDP function switch

3. Configure the operating state of port LLDP

4. Configure the intervals of LLDP updating messages

5. Configure the aging time multiplier of LLDP messages

6. Configure the sending delay of updating messages