KahoILoveMarket

Answer by GTB
Let's review and define because I suspect the problem is rooted in understanding basic hardware.

1. A "strict" modem ("strict" meaning a modem not a hybrid which is defined below) converts a carrier's signal (DSL from phone company, CATV signal from cable tv carrier) into an Ethernet protocol signal; this feed has its own public (routeable) IP address and feeds one and only one downstream device.

2. A router (gateway router in this case) has a single WAN and single LAN port. The modem's internet feed with the carrier provided public IP address connects to WAN port. The LAN port has a different, private, nonrouteable IP address in a different subnet. Routers include firewall functionality. A router enables many LAN devices with non-routeable IP addresses to interface with each other and access internet.

3. A network switch has no IP address. It functions as a "junction block" where the router LAN feed and all other network devices interconnect. A switch is NOT a router and it cannot by itself enable LAN devices to share an Internet conection.

4. Wireless access point - this LAN device provides wireless capability.

5. Now for the hybrids

5a. There are many switch / routers where the router and a 4 port LAN switch are integrated into a single unit. If more switch ports are needed, a network switch is added. With a switch / router and no added network switch, 4 LAN devices are interconnected and can share internet.

5b. There are switch / router / wireless access points often called a wireless router. This is usually a 4 port switch + wireless access point on private side + the normal wan feed.

Now I suspect that you have

1. A "strict" modem

2. A network switch

3. no router.

This is why you have a problem; you need a router between network switch and modem.