Is the server for the intranet to be hosted by Lunarpages? If not, please do not ask questions here about non-LP implementations.
If your intranet is to be on an LP-hosted server, but accessible only within your company, I don't know what the setup would be. You'd have to ask support -- maybe they have some experience with this sort of thing. If you want a website that is accessible to both the Internet (public) and your company (private), I would think that you'd simply set it up as a normal website, and do something within the company to make sure it isn't blocked. Are you looking for some sort of access control to give expanded in-company access to the website (or conversely, restricting access by the public to certain parts of the site)? In that case, it might be better to have some sort of ID and password control on a "w3" (for example) subdomain for internal areas.