I have my main computer (iMac) and an iBook using airport connected to COMCAST. I use a router. COMCAST Cable coming in goes to their modem, then to the router. I plug my imac into the router and my Airport base into the router. In checking with COMCAST, they advise this is OK, I can use as many computers as I want, as long as I only use the one modem. I hope this helps Norm_M