Do I need a router, or will a cable modem + switch do?

I think the WAN/routing side of my cable router is knackered... Assuming the LAN side is okay, can I just connect my cable modem to 1 of the 4 LAN ports - effectively making it a wireless switch? If so, is it just plug & play or is some configuration required?

Cheers, James

Only one computer can go online that way

Thanks Andrew

Then how come when you connect a switch to a router, that switch then provides multiple simultaneous connections? i.e. If I attach an 8 port switch to a 4 port router, that effectively gives me 11 active ports. Is this not the same thing?

Thanks again, James.

"Then how come when you connect a switch to a router, that switch then provides multiple simultaneous connections?"
All the data between the WAN side and LAN are routed through the router which sorts out where incoming and outgong data packets go.
The cable modem presumaby has no routing capability, so is unable to handle multiple LAN conections on its own