I am looking to build a transparent firewall with proxy arp so that internal boxes can use public IPs. I have been using the LEAF mountain series and switched to Dachstein about 5 months ago. I have been trying to read up on the Bering LEAF system which is a derivative of Dachstein. Bering uses Shorewall.
Looking at the diagram of your system I am interested in how your workstations have both a private IP and a public IP as you describe and diagram here: http://www.shorewall.net/myfiles.htm Victor McAllister
