Category 5 network cables have eight wires, but only four of them are used. Two are used to transmit data and two are used to receive data. You can create either a straight through cable or a cross over cable. A straight through cable can connect a Ethernet hub to a computer's network adapter, whereas a cross over cable can connect two Ethernet hubs or two computers together via their network adapters.
RJ-45 Straight Through Connector
For a straight through cable, both ends are wired the same. With the tab facing down and going from left to right, the color code is orange/white, orange, green/white, blue, blue/white, green, brown/white, brown. The following diagram depicts the correct wiring order for a straight through cable.
RJ-45 Cross Over Connector
For a cross over cable, one end of the cable is wired as above and the other end is wired as follows: With the tab facing down and going from left to right, the color code is green/white, green, orange/white, blue, blue/white, orange, brown/white, brown. The following diagram depicts the correct wiring order.