mac,pc, ethernet

Hi,just got dsl with wire modem. Put the software into Toshiba laptop
and works aok. I also have a mac cube-thought I needed software
install for it, but was told to just plug in the ethernet cable.
I did-and it worked.
Now, I unplug one cable and put the other into the modem when I
switch computers. My question is: can I put a splitter in the modem
and run the two cables into that so I don't have to unconnect-connect...
I'll be online with either one or the other. Could there be a conflict
even if used like this? Tweet