link speed $ Duplex

the default automatically adjust the speed so what is the Duplix for??

Sometimes for various reasons, network guys set the switch port for different settings. Normally automatic will auto adjust your card settings accordingly, but lets say you have to set something manually which is primarily done in data centers on servers. Full duplex is a term that is used to describe a device that can talk on the network two ways at the same time, say like a telephone. Half duplex refers to a term where a device can talk on the network two ways but only one way at a time, itcan talk or listen but not at the same time, like a walkie talkie. HTH.