Depending on what your connection is, I wouldn't advise disconnecting your modem and moving it very often, as it will drop sync and might react to it as a fault and maybe lower your profile if your on a MAX connection for example. I don't know if that affects adsl2 or not.
For the above comment on the using the phone line, its pins 1,2,3 and 6, ie the green and orange pairs. See http://en.wikipedia.org/wiki/Ethernet_crossover_cable
<- note thats a cross over, wikipedia seems to tihnk straight dosn't need showing. Most PC's and switches are auto cross anyway, so either do it both ends the same (PC to a switch) or one of each (switch to switch).