The Case 1:

We have a IP range in our local network which reserve for 4 virtual machine which run our demo product and can be managed directly by developer when they need to show case to our customer. 

Problem is every time they want allow outside access to their demo product i have to add new record to Nginx or router to forward the request to demo server and now i go tired with that task. I want nginx to extract the forward destination by reading the domain information and forward request to that. For example, when user request http://acceptance01.8080.example.net/index.php Nginx will forward lookup local DNS for computer name acceptance01 and forward to that computer on port 8080 with file index.php. If request failed some how Nginx will handle the bad situation by display a nice error message.

Here is some quick and dirty config from my /etc/nginx/sites-available/vm.example.com

server {
    listen   80;
    server_name  *.vm.example.com;

    # Point this to you DNS server which client get DHCP from
    # for example: a virtual machine with host name "abc" request DHCP with your router
    # the DNS name will remember the IP address of "abc" in memory that why we can use
    # hostname with style of abc.vm.example.com
    resolver 192.168.1.1;

    set $realservername "";
    set $realport "80";

    if ($http_host ~ ^([a-z0-9\-]*)\.(vm\.example\.com)$) {
        set $realservername $1;
    }

    if ($http_host ~ ^([a-z0-9\-]*)\.(\d*)\.(vm\.example\.com)$) {
        set $realservername $1;
        set $realport $2;
    }

    location / {
        # Block client if client not from my country
        # if ($geoip_country_code !~ (VN|^$) ) {
        #    return 403;
        # }

        # uncomment this if you want to limit the name list of server name
        # if ($realservername !~ (name1|name2|name3) ) {
        #    return 403;
        # }

        proxy_connect_timeout 10s;
        proxy_read_timeout 20m;
        proxy_send_timeout 20m;
        proxy_pass  http://$realservername:$realport;

        # needed to forward user's IP address to rails
        proxy_set_header  X-Real-IP  $remote_addr;

        # needed for HTTPS
        proxy_set_header  X-Forwarded-For $proxy_add_x_forwarded_for;
        proxy_set_header Host $http_host;
        proxy_max_temp_file_size 0;
    }
}