On my old linux system I was using some custom firewall rules. (small part of what was in the rc.firewall.local file) The reason I did this was because I have 8 IP's that I wanted to use. (1 for DNS (NS1) server, 1 for DNS (NS2) server, 1 for email, 1 for FTP etc. etc.) Is there a way of setting this within the ISPConfig firewall (runing on Fedora core 4) ?
No, but you don't have to use the ISPConfig firewall and can continue using your own rules (but make sure you don't block port 81...).