3Com 5500 SI - Switch - Stackable, Configuration Manual

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5
DLDP C
ONFIGURATION
This chapter contains DLDP overview, fundamentals, precautions during
configuration, and configuration information.
DLDP Overview
You may have encountered unidirectional links in networking. When a unidirectional
link occurs, the local device can receive packets from the peer device through the link
layer, but the peer device cannot receive packets from the local device. See Figure 20
and Figure 20. Unidirectional links can cause many problems, spanning tree topology
loop for example.
Device Link Detection Protocol (DLDP) can detect the link status of the optical fiber
cable or copper twisted pair (such as super category 5 twisted pair). If DLDP finds a
unidirectional link, it disables the related port automatically or informs users to disable
it manually depending on specific configuration, to avoid potential network
problems.
Figure 19 Fiber cross-connection
Figure 20 Fiber correct connection/disconnection in one direction