by John Andrewartha.
OK so all the equipment you can get at.
The very simplest way is to get a small IP allocation from your provider.
If that is not possible then how have you set up your network?
EG router with 1 IP and you have to setup virtual hosts that have private IP addresses
IE [public IP port 80 >> private IP port 80] for your Moodle or have you given the Moodle machine the public IP address?
Remember you can not have two machines on a network that have the same IP address either public or private.