To do this, you need to set up the linking of LAN ports in OS X as mentioned earlier then you need a 10/100/1000/2000 switch.
They have several on newegg but this is the most reasonable priced: http://www.newegg.com/Product/Product.asp?Item=N82E16817111479
They have several on newegg but this is the most reasonable priced: http://www.newegg.com/Product/Product.asp?Item=N82E16817111479