internal redirection

I have a server machine with a servlet engine running on it and a firewall with Apache. The firewall will be serving all the HTML and the server machine will run the servlets. I've been looking for a way to route a specific URL (such as http://www.myfirewall.com/servlet/myServlet) from the firewall to the server machine to execute but I've been having some difficulty learning how to use mod_rewrite. My server machine has an internal ip address so I can't use an external redirect. The only other solution I know of is to use ipchains on the firewall to redirect a certain port to the server, but all in all that's a bigger security hole. Any help is greatly appreciated.

Aaron Braeckel