A Reverse Proxy Scenario
Company example.com has a website at www.example.com, which has a
public IP address and DNS entry, and can be accessed from anywhere
on the Internet.
The company also has a couple of application servers which have
private IP addresses and unregistered DNS entries, and are inside the
firewall. The application servers are visible within the network -
including the webserver, as "internal1.example.com" and
"internal2.example.com", But because they have no public DNS entries,
anyone looking at internal1.example.com from outside the company
network will get a "no such host" error.
A decision is taken to enable Web access to the application servers.
But they should not be exposed to the Internet directly, instead they
should be integrated with the webserver, so that
http://www.example.com/app1/any-path-here is mapped internally to
http://internal1.example.com/any-path-here and
http://www.example.com/app2/other-path-here is mapped internally to
http://internal2.example.com/other-path-here. This is a typical
reverse-proxy situation.
