So, I'm having a play with IPTables, with the aim of getting rid of our ISA box (there's no need to pay for a proxy!)
The thing that is odd about our network is this - it is a single port 'firewall', as we are on a WAN.
So, what I'd like to do is this, port forward all requests for port 80 to another web server. I have the following rules in the iptables.up.rules file in /etc/ (created via webmin):
-A PREROUTING -p tcp -m tcp --dport 80 -j DNAT --to-destination 10.5.143.125:80
-A FORWARD -p tcp -m tcp -d 10.5.143.125 --dport 80 -j ACCEPT
Yet, when I navigate to the that machine in a browser, nothing happens. It just hangs.