See the response using mod_proxy.
To explain it a bit more the way it works is this.
You have an IP, lets call it 18.104.22.168 associated with your main apache server, you then have several other servers/sites on internal ips, say 22.214.171.124 and 126.96.36.199 for another one.
You setup your site so that you can request them as such:
You will then go into your apache configuration file, traditionally httpd.conf, and enable a 'ProxyPass' to get those to the right location.
ProxyPass /site2 http://188.8.131.52
Proxypass /site3 http://184.108.40.206
Now your main Apache server sees an incoming request for 220.127.116.11/site2, it reads it's configuration file and sees that any request on /site2 should be forwarded, or proxied
, to http://18.104.22.168