This is following on from setting up Smoothwall with BT Infinity – https://www.linuxtutorial.co.uk/smoothwall-express-bt-infinity-setup/
The issue I now had was giving our network a static IP address instead of Dynamic. This was to allow another host to allow a static IP through their Firewall.
The workaround for this was to assign an External (red) IP address to an Internal (Green) IP address.
BT will provide 5 extra static IPs for £5 per month.
To set this up:
1. Full Firewall – Multiple IPs
2. Set the required external red IP and the IP of the internal machine