Use XP machine as a firewall
Posted on 2005-04-04
I was asked last week to set up an internet connection at my friend's company using a spare XP machine with two network cards as a firewall between the LAN and the ADSL Modem. Because of the crap router provided by BT which is totally unconfigurable, I tried setting it so one network card was on the same IP subnet as the LAN, the other was configured to the static IP required by the router, end then trying to create a link between the two, passing through Sygate Professional firewall.
Microsoft's Internet Connection sharing worked, but was not good enough for me as it imposed a different subnet which meant that they could not then access other systems which were IP dependent.
After two days of trying various things I eventually persuaded him to buy a decent configurable ADSL router with built in firewall and leave the XP machine out of the equation. After 5 minutes configuration it was up and working perfectly.
How could I have set the machine up, without extra software such as a proxy server?
The card connected to the router needed to be a specific address (lets say 18.104.22.168 - not the real one), while the lan was set up on the 192.168.1.xxx addresses