360 and ps3 ip address problems

Hello,
okay primarily im trying to get interntet on to my ps3 n 360. i have a wired modem so i jus switch the ethernet cord from my computer to the game system. but now its failing the ip address test n i learned that its because i need to go to the network options n share the connection but when i cut it on to share the internet on my computer goes away n it still does not work on the game system. n e answers?