I've got a fairly standard home network with a modem from my ISP, which is connected to a router which then provides NAT to about 3 PCs and laptops. There's a possibility to obtain one public IP from my ISP.
Now I'd like to add a web server to this setup. What I'm concerned about is how the web server will play along with the rest of the network.
Say that my ISP gives me a public IP address of 1.2.3.4. In my home router, I think that I'll need to setup a rule saying that requests to 1.2.3.4:80 should be routed to my web server's internal IP, say 192.168.1.1.
However, if I sit at my home PC and try to load google.com, Google will probably see my PC's IP (which might be 192.168.1.2) as 1.2.3.4 (my public IP) and will send the response to this IP. When the IP packets reach my router, it will see it as a packet to 1.2.3.4:80 and I'm worried that it will be routed to my home web server which would obviously prevent my PCs from working correctly.
I'm sure there's some hole in the reasoning above and that it is possible to have both regular desktops and a web server behind one public IP. So if anyone could explain where my thinking is wrong and how it really works, it would be greatly appreciated.