trouble setting up xbox live

i'm having problems getting the IP address to register on my live connection. i connected the cable to the back of my computer and to the back of the system and its not registering a connection. we also have a motorolla cable box extension that has room for 1 connection port. i've tried connecting the cable to both apparatuses but no matter what i do i'm still not getting a connection to xbox live. can anyone help me figure this out?

you need to make sure the box is on the same network, just plugging in the cable wont be enough, unless you have dhcp enabled on the router/pc, depending on your setup. It doesnt make sense to me, maybe you could be more specific.

like.:

modem -> pc -> 360 or modem -> pc
                                              -> 360

on the computer:

control panel

network connections

local area connection 1 (left click)

local area connection 2 (hold shift and right click)

left click bridge connections.

for a modem -> pc -> xbox connection the bridge is a must.  then you'll be able to go on halo 2 and tell people youre bridging!!!