3Com 4210 9-Port Configuration Manual page 190

# Set the DLDP handling mode for unidirectional links to auto.
[SwitchA] dldp unidirectional-shutdown auto
# Display the DLDP state
[SwitchA] display dldp 1
When two switches are connected through fibers in a crossed way, two or three ports may be in the
disable state, and the rest in the inactive state.
When a fiber is connected to a device correctly on one end with the other end connected to no device:
If the device operates in the normal DLDP mode, the end that receives optical signals is in the
advertisement state; the other end is in the inactive state.
If the device operates in the enhance DLDP mode, the end that receives optical signals is in the
disable state; the other end is in the inactive state.
# Restore the ports shut down by DLDP
[SwitchA] dldp reset
2) Configure Switch B
The configuration of Switch B is the same to that of Switch A and is thus omitted.
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