Virtual server with two different web servers

No, it is not. The process is as follows: Server1 receives initial web request, upon this request it forwards to server2 for authentication, then forwards back to Server1, where the rest of the web traffic will be taken place.

I am stuck at where server1 directs to server2, it is using an internal address, which externally is not resolvable, so I get a server cannot be found error. I need all this address translation to happen behind the virtual server, not a redirect to a server2 which is not accessible via the internet with it's name.