Mediawiki Fix Internal Server Host Names / Redirection In shared Hosting or Proxy Setup

Our customer support wiki runs on an internal host (ip:192.168.1.100:300, hostname a-node100.:300) and it is behind the nginx reverse proxy server. However, our Apache server end up displaying internal server name http://a-node100.:300/, which results into an unexpected redirection and timeouts as http://a-node100.:300/ is not accessible over the Internet. How do I force nginx or apache to use the base URL of our server (http://support.example.com/wiki/)?

Read answer to: "Mediawiki Fix Internal Server Host Names / Redirection In shared Hosting or Proxy Setup"