Problem with DNS and/or Virtual Host (works from inside, not from outside)

Question

I am running several web sites (as virtual hosts) successfully on one Xserve (192.168.200), which are accessible internally and from the Internet (via forwarding port 80 on our firewall).
Now I am trying to add another web site (newmini.domain.com), which however is running on a Mac mini (also on the same subnet as the Xserve) at 192.168.100. What I did is make an additional entry under the Xserve's DNS for the domain (domain.com) (+ Machine..., pointing to 192.168.0.100). (I also made the necessary changes to the Mac mini's httpd and hosts configuration--no problem there).
Now, here's the strange thing: All computers on the subnet, whose DNS points to the Xserve, can see and browse newmini.domain.com fine. No problem. The computers ask the Xserve for the IP of the host in question, the Xserve says, "192.168.100", the request goes to the Mac mini, and it serves the web site as expected.
But this doesn't happen if the request comes from the Internet. Instead of seeing the Mac mini, the client sees the default web site of the Xserve... So it appears that somewhere, the virtual host part of the HTTP request is lost between our firewall and the Xserve.
Any ideas? Thanks.

Answer 1

It's not going to.
You say you've setup port forwarding on the firewall. Port forwarding only cares about the port number (80). It knows nothing about the nature of the request (e.g. the hostname that the web request is for). Therefore all extenal connections on port 80 get sent to the XServe. The newmini doesn't see the traffic at all.
If you only have a single public IP address you can only forward port 80 traffic to a single machine. Your options are to either use a different port number, or configure the XServe to proxy the connection to the mini (so now the traffic goes router -> XServe -> Mini -> XServe -> router), although that might not do what you want since it still places load and dependencies on the XServe.