First, I apologize. I searched on "reverse proxy" and I can see this topic has been beat to death, but for the life of me I cannot find the answer I'm looking for. So here goes: I presently have a setup that looks like this: External Firewall with a Static External IP (38.x.y.z) and Internal IP (192.168.a.a) points to an internal Apache reverse proxy server (192.168.a.b) The Apache Reverse Proxy server points to a number (probably 3-5) servers internally that run their own software and web servers. In other words, I don't control their content. For instance, one is a Ubiquiti UniFi controller, which runs on it's own Tomcat + Java stack. Another points to an ESET Management Server, which runs on its own NGINX + Postgres stack. Then I have a LAMP server or two. What I'd like to have is this: External Firewall with a Static External IP (38.x.y.z) and Internal IP (192.168.a.a) points to an internal ISPConfig reverse proxy server (192.168.a.b) For the sites that are LAMP stack based, they can just live on this server, and I can assign them IP addresses internal to the ISPConfig server, creating my own non-routable subnet there. This could be 127.0.0.3-127.0.0.255, or something completely unique like 172.20.15.2-172.20.15.254. For the servers that are not LAMP stack based, a redirect exists that handles both HTTP and HTTPS. So those would redirect to, say, 192.168.a.p, where a.p is a valid internal IP pointing to say the UniFi controller, for instance. What I've been having trouble with is the ISPConfig GUI configuration for this second scenario. I can make the LAMP Stack based sites work through the GUI, no problem. But I can't make the ISPConfig server redirect to an internal IP address via apache reverse proxy commands. Under Sites in the ISPConfig interface, I've tried using the Redirect Type=proxy and the Redirect Type=R=301,L settings. I've also checked and unchecked the Rewrite HTTP to HTTPS checkbox. I've also read and followed a Stack Overflow post where the OP suggested just skipping all of this and going to the Options tab and pasting in my Apache Directives straight in (that didn't work). I did also, also try using the "Enable Proxy Protocol" checkbox there. So, with all that said, I'm fully expecting someone to tell me the RTFM (that I can't find specifically covering this use case) and the answer should be obvious, but well, it's not, at least not to me. Can someone humor me and tell me what I should be doing here? If needed, I can post a sample of my existing Apache Reverse Proxy server configuration that works (but isn't ISPConfig). Thank you, in advance!