Using RHEL 8.x and Apache Web Server, I tried modifying httpd.conf. I based my modifications on this Apache website. But my results were that in the web browser I saw "Service Unavailable." If I bypassed the Apache web server, the destination web server works fine. I accessed the destination server with an IP address. How do I configure Apache web server to be a reverse proxy server? (I know I have to modify the httpd.conf file. But using "proxypass" variations in the syntax of the above link did not work for me. I just see "Service Unavailable.")