rdr to another machine and back

["Lawrence Farr" <freebsd-isp@xxxxxxxxxxxxxxx>]

Hi,

I'm trying to work out how to get a gateway machine 
to send all http requests to a separate machine and
get them back, network looks like this:

   internet
    	|
	|
    router-----------http_proxy
	|			|
	|			|
	----internal-------

So the router has 3 interfaces, one to the outside
world, one externally available network and one 
internal. The proxy has 2 interfaces one to internal
and one externally available. I can redirect port 80 
to a proxy on the router without any issue, but want 
to send them to the separate proxy machine. Has anyone 
done this, or does anyone know of a howto?

Many thanks

Lawrence Farr