Hi > I am pulling my hair out with this. I have a single public IP and already > have a web server redirected on the firewall from the external IP to the > private IP of 10.5.36.5. Now I need to enable another box (10.5.36.6) > running on port 80 to be accessible from the outside. 10.5.36.6 is a physically separated server, isn't it (you said "another box")? If it's the case, it has nothing to do with mod_rewrite, only with your firewall (I suppose that you only have one unique public ip address). You need to configure your firewall to forward requests made oon port 81 to 10.5.36.6:80. Regards, Gaël