Forwarding to Other IP's ??

I have a few questions about forwarding to other internal IP addresses.

This is my setup

***.***.***.2 - Network Security Server
***.***.***.3 - Network Security Probe
***.***.***.6 - ISPConfig Server #1 Primary IP
***.***.***.7 - ISPConfig Server #1 Secondarly IP
***.***.***.10 - ISPConfig Server #2 Primary IP
***.***.***.11 - ISPConfig Server #2 Secondarly IP

ISPConfig Server #1 Is the only server accessable from the Internet. How can I setup Server #1 to control Server #2 so that I can use it for hosting as well? And how can I setup a subdomain and forward it to the Network Security Server, so I can access it from the Internet as well?

Thanks for any help you can offer me.

 

PS : IP with the same Colors are on the Same Server.

 

You could set up a reverse proxy on your ISPConfig server:
http://httpd.apache.org/docs/2.0/mod/mod_proxy.html
http://cwiki.apache.org/GMOxDOC20/configure-apache-httpd-as-a-reverse-proxy-modproxy.html