User's Manual

AT-9000 Gigabit Ethernet Switch Installation Guide
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 If a switch port is using Autonegotiation (the default setting) to set
its speed and duplex mode settings, the end node connected to
the port should also be using Autonegotiation to prevent a duplex
mode mismatch. This can occur because a switch port that is using
Autonegotiation will default to the half-duplex mode if it detects that
the end node is not using Autonegotiation. If the end node is
operating at a fixed duplex mode of full-duplex, the result will be a
mismatch of settings on the two devices, with the switch port using
half-duplex and the end node using full-duplex. To avoid this
problem, you should disable Autonegotiation on a switch port and
set the port’s speed and duplex mode manually if the end node has
a fixed duplex mode of full-duplex.