How do you connect your PS3 online with an ethernet cable and cable modem?

You purchase a router and connect it to the cable modem and then connect everything to the router. Otherwise you have to unplug whatever is connected to the cable modem (for example a PC) and plug in the PS3 . Whatever you have unplugged is no longer connected to the internet until you unplug the PS3 and plug it back into the modem. Once the PS3 is connected to the cable you need to go to network settings on the PS3 and set up the network connection.