Ethernet port is not recognized, even though it is on the motherboard.?

I have a motherboard in my custom computer it is a ASUS P5G41-M LX2/GB. It has a ethernet port but when i plug a cable in it doesn't do anything. I looked in Network Connections and there is not even an icon for it. I have also looked at device manager, shown all hidden and it still does not show. Am i missing something or is there something i can download so that it works?