|BTW you need a router not a switch. |
I agree completely with what wanderer said.
In your specific case, buy a router with 4 LAN ports. Connect the internet to the WAN port and your client computers to LAN ports. Set the network interfaces on your laptop/PC to get their TCP/IP settings automatically (DHCP) and the router should give them IP's that will allow them to talk to each other on the LAN as well as have internet access.
No more messing around with IP addresses.
If you have more computers than 4, you connect the switch to a LAN port and plug clients in to it. For all intents and purproses, it's invisible and clients plugged into it will still get their IP address from the router's DHCP server and have both LAN and WAN access.
It matters not how straight the gate,
How charged with punishments the scroll,
I am the master of my fate;
I am the captain of my soul.