you can't just use any old ethernet cable - it must be a crossover type. You should be able to buy one at any decent computer store.
In normal ethernet cables the wires are connected 'straight through' that is, each wire is connected to the same Pin number at each end of the cable. There is always some confusion over crossover cables, and for the record, this is the order in which the cable conductors are connected inside the RJ45 plug - should you feel inclined to make your own. The colours quoted for each pin are those normally used, but of course you can use any colours you like - the cable doesn't know which colour is which - as long as the Pin crossover order is the same (Pins 1&2 transmit, and Pins 3&6 receive).
Here's the wiring order:-
(Pins 4,5,7,and 8 are not used).
Pin 1 at one end (orange/white) becomes Pin 3 at the other.
Pin 2 (orange) becomes Pin 6
Pin 3 (green/white) becomes Pin 1
Pin 6 (green) becomes Pin 2