AT-9000 Gigabit Ethernet Switch Installation Guide
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.
