Duplex Mismatch Explained
Still one of the major problems in most networks is a mismatch in the duplex settings between the switch port and the connected device. This video provides a detailed explanation of the problem and shows screen shots using the Fluke Networks EtherScope.
Forcing the duplex to Full on one side and leaving the other set to Auto will result in network slowdowns. To see why this happens, click on the video below.