Internet sharing using a switch

If the modem is a simple on it has to be connected to a computer to work as it gets it's management and control instructions from the computer - think of it as a simple phone. This type can NOT be shared direct, the computer it's attached to has to be set up for internet sharing and it must act as a gateway fro the other computers, that is done by hooking them into the switch.

In effect one computer contacts the internet through the modem and the other one contacts the internet by going through the first computer.

If you have a modem / router that maintains the contact with the ISP, then you should be able to set it up as the gateway and just hang the switch behind it with everything off the switch once you point them at the modem / router acting as the gateway.

You need to tell us what type of modem and internet connection you have before we can make an intelligent appraisal.

I use ADSL and have a modem / router which manages the internet connection, that connects to a switch which is also connected to four PCs. The Modem / Router has an internal IP address of 192.168.0.1 (this is a reserved address that does NOT work on out in the Internet itself, but works within my LAN) and the PCs look to it as a gateway and DNS server. It works perfectly, but you do have to set up the network connections on each PC to do it and you need a suitable modem / router.