SNR S2989G-48TX-POE — настройка ULDP для предотвращения проблем с сетевыми соединениями [76/553]

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2-12

Switch B

g1/0/1

g1/0/2

S2989G-24TX Operation Manual Chapter 2 Layer 2 services

Configuration

Switch A

g1/0/3 Switch C

Figure 2-5 One End of Each Fiber Not Connected

This kind of problem often appears in the following situations: GBIC (Giga Bitrate

Interface Converter) or interfaces have problems, software problems, hardware becomes

unavailable or operates abnormally. Unidirectional link will cause a series of problems,

such as spinning tree topological loop, broadcast black hole.

ULDP (Unidirectional Link Detection Protocol) can help avoid disasters that could

happen in the situations mentioned above. In a switch connected via fibers or copper

Ethernet line (like ultra five-kind twisted pair), ULDP can monitor the link state of physical

links. Whenever a unidirectional link is discovered, it will send warnings to users and can

disable the port automatically or manually according to users’ configuration.

The ULDP of switches recognizes remote devices and check the correctness of link

connections via interacting ULDP messages. When ULDP is enabled on a port, protocol

state machine will be started, which means different types of messages will be sent at

different states of the state machine to check the connection state of the link by

exchanging information with remote devices. ULDP can dynamically study the interval at

which the remote device sends notification messages and adjust the local TTL (time to live)

according to that interval. Besides, ULDP provides the reset mechanism, when the port is

disabled by ULDP, it can check again through reset mechanism. The time intervals of

notification messages and reset in ULDP can be configured by users, so that ULDP can

respond faster to connection errors in different network environments.

The premise of ULDP working normally is that link works in duplex mode, which

means ULDP is enabled on both ends of the link, using the same method of authentication

and password.

2.4.2

ULDP Configuration Task Sequence

1. Enable ULDP function globally