You mean on all that IPs mentioned above you got a webserver running that shall server some pages in the internet?
At first you have to forward port 80 / 443 from your internet access (e.g. dls router) to _one_ of the machines. you can not forward port 80 e.g. to machine a or to machine b depending on the request.
An alternative would be to use mod_proxy on one machine, that's accessing, depending on the URL / URI, the backendservers accordingly.
But when using mod_proxy, the only thing that you need is the textarea in the web's config