PS3 Ip adress error?

I get my modem up working, I put my Ethernet cable into it, Instead of putting it into the computerI put it into the ps3. I then turn on my ps3, go to settings and do wired connection. I do everything custom and everything set to automatic, when I do the test thing it wait's like 30 seconds and then says " Attempt to collect the IP adress failed." or something like that... How do you fix this? I just got Avatar and Uncharted 2 just for multiplayer since I beat them both... Can you please help?

I get my modem up working, I put my Ethernet cable into it, Instead of putting it into the computerI put it into the ps3. I then turn on my ps3, go to settings and do wired connection. I do everything custom and everything set to automatic, when I do the test thing it wait's like 30 seconds and then says " Attempt to collect the IP adress failed." or something like that... How do you fix this? I just got Avatar and Uncharted 2 just for multiplayer since I beat them both... Can you please help?

NomNomNomNoNom

I get my modem up working, I put my Ethernet cable into it, Instead of putting it into the computerI put it into the ps3. I then turn on my ps3, go to settings and do wired connection. I do everything custom and everything set to automatic, when I do the test thing it wait's like 30 seconds and then says " Attempt to collect the IP adress failed." or something like that... How do you fix this? I just got Avatar and Uncharted 2 just for multiplayer since I beat them both... Can you please help?