Hi Winan,
I use a Linksys 4 port switch Router to handle my Network Address Translation (e.g. NAT). Its great and easy to configure. It cost me around $140.00 US about three years ago, but it can be purchase today for around $60 or $70 US. I configure the router with the static IP address assigned to me by my ISP. The Router acts as a firewall, so anyone in the internet would only be able to see the static IP address assigned by my ISP. The local network is completely hidden behind the router.
The router can be easily programmed using a browser GUI. Using the browser, I connect to the router and enter the static IP address and Domain Name Server addresses supplied by my ISP and the gateway address to be used by all the computer in the local network. I use a 192.168.1.1 address for the gateway. I can click on a tab in the browser and a window will be openned that allows me to assign forwarding address over various ports. All packet my router received from the internet that have my static IP address as the destination for port 80 are forwarded to a local IP network address for the computer that runs my web server as follows:
Forward to
App Ext Port Int Port Portocol IP Address Enabled
--- -------- -------- -------- ------------- -------
http 80 80 TCP/IP 192.168.1.78 Y
postgres 5432 5432 TCP/IP 192.168.1.117 Y
As you can see above, packets received for postgres are forwarded to the computer running the database server with local network IP address of 192.168.1.117.
Using the router really makes things easy. There are many other freatures of the Router that I'm not currently using like filtering. If I purchase a router today, I think I would pay a little extra to get one that also provided a VPN.
Below are a couple of Links that may be of help to you if you decided to use your Linux computer as your proxy, firewall, router and NAT.
http://www.netfilter.org/unreliable-guides/NAT-HOWTO/For the link below look for the article titled "Quick and Easy Linux NAT Gateway"
http://www.networknewz.com/2002/0424.htmlLelandJ
