Configure multiple webservers on IPCop

I am using IPCop using the red/green/orange configuration.  There is currently one webserver on the orange interface configured like this:

IP 172.30.30.11
Subnet 255.255.255.0
Gateway 172.30.30.1

I am trying to add a second webserver but cannot seem to get internet access on this second machine.  I have configured the second webserver like this:

IP 172.30.30.12
Subnet 255.255.255.0
Gateway 172.30.30.1

but this second machine cannot get online.  

Presently under port forwarding I have rules which forward traffic to 172.30.30.11, but there are no entries at all that refer to my proposed new server at 172.30.30.12.  When I try to add another rule to forward traffic from port 80 to the new server at 172.30.30.12, I get an error saying "Source port in use: 80".

Is what I am trying to do even possible?  What entries do I need to make to the IPCop configuration to allow a second webserver to be online at the same time as the original one?  

Thank you.
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