Конфиг фронтенда:

server {
    listen xx.xx.xx.xx:80;
    server_name *.example.ru;

    access_log off;
    error_log /var/log/nginx/example.ru.error.log crit;

    location / {
        client_max_body_size 32m;
        proxy_max_temp_file_size 0;

        proxy_pass http://11.0.0.24:80;

        proxy_set_header    X-Real-IP       $remote_addr;
        proxy_set_header    X-Forwarded-For $proxy_add_x_forwarded_for;
        proxy_set_header    Host            $http_host;
        proxy_set_header    X-NginX-Proxy   true;

        proxy_redirect off;
        port_in_redirect off;
    }
}