3com 5500-SI Manual De Usuario

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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