First-time poster, so bear with me.

I'm relatively new to Nginx, but have managed to figure out what I've needed... until now.

Nginx v1.0.15 is proxying to PHP-FPM v.5.3.10, which is listening at http://127.0.0.1:9000. [Knock on wood] everything has been running smoothly in terms of hosting our CMS and many websites.

Now, we've developed our CMS and configured Nginx such that each supported website has a preview URL (e.g. http://[WebsiteID].ourcms.com/) where the site can be, you guessed it, previewed in those situations where DNS doesn't yet resolve to our server, etc.

Specifically, we use Nginx's Map module (http://wiki.nginx.org/HttpMapModule) and a regular expression in the server_name of the CMS' server{ } block to 1) lookup a website's primary domain name from its preview URL and then 2) forward the request to the "matched" primary domain.

The corresponding Nginx configuration:

map $host $h {
    123.ourcms.com  www.example1.com;
    456.ourcms.com  www.example2.com;
    789.ourcms.com  www.example3.com;
}

and

server {
    listen              [OurCMSIPAddress]:80;
    listen              [OurCMSIPAddress]:443 ssl;
    root                /var/www/ourcms.com;
    server_name         ~^(.*)\.ourcms\.com$;
    ssl_certificate     /etc/nginx/conf.d/ourcms.com.chained.crt;
    ssl_certificate_key /etc/nginx/conf.d/ourcms.com.key;

    location / {
        proxy_pass http://127.0.0.1/;
        proxy_set_header Host $h;
        proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;
    }
}

(Note: I do realize that the regex in the server_name should be "tighter" for security reasons and match only the format of the website ID (i.e. a UUID in our case).)

This configuration works for 99% of our sites... except those that have a dedicated IP address for an installed SSL certificate. A "502 Bad Gateway" is returned for these and I'm unsure as to why.

This is how I think the current configuration works for any requests that match the regex (e.g. http://123.ourcms.com/):

1. Nginx looks up the website's primary domain from the mapping, and
2. as a result of the proxy_pass http://127.0.0.1 directive, passes the request back to Nginx itself, which
3. since the proxied request has a hostname corresponding to the website's primary domain name, via the proxy_set_header Host $h directive, Nginx handles the request as if it was as direct request for that hostname.

Please correct me if I'm wrong in this understanding.

Should I be proxying to those website's dedicated IP addresses? I tried this, but it didn't seem to work? Is there a setting in the Proxy module that I'm missing?

Thanks for the help.

MB