Private WAN to Public WAN

I have a situation where I must route two PPP WAN interfaces together - I am sure it is just a routing issue, but I only half-way understand routing tables. Here's the situation: WARNING: You don't even want to know why I have two PPP WAN interfaces in one PC that must be routed to each other - trust me!)

Anyway, modem 1 in laptop 1 dials out to the internet (a public WAN). Modem 2 in laptop 1 is dialed into from laptop 2 through a line simulator. I need to be able to reach the internet from laptop 2 through its DUN to laptop 1; however, this WAN has a private non-routable IP.

I am sure this is networking 101 for pro's - essentially it is just routing the two PPP WAN's in such a way that they communicate - like bridging, but I don't think I can route the private WAN, can I.

Laptop 1 is Win 2k and Laptop 2 is Win XP - so the question is this: is it possible to route the private WAN to the public WAN and how do I accomplish that?

Again, any help would be appreciated!

 

I have editied the original post and hope it is more meaningful both in title and content.
STEVE: pc anywhere, VPN and remote desktop sharing all allow me to control laptop1 from laptop 2, but that is not what I am attempting. I simply need to use laptop 1's connection to the internet for laptop 2. I realize there are simpler ways to accomplish this using NIC's (ICS); however, the connection between laptops must be through modems.

I posted earlier about how "ugly" this thing was that I was working on, so in order to give everyone the "thousand-mile" view; here are the ugly details.

I have a Direcway 1-way system. That is a satellite delivered Internet solution for those unfamilier with it. This system uses a modem for outbound traffic and satellite for the returns. I live remotely and satellite is the only option for cost-effective broadband. The problem is the outbound - not the speed, but the cost. It is less expensive to use GPRS for the outbound, better speeds, flat rate, no ISP, etc.

The root cause of not being able to use a cell phone as the outbound modem has to do with the client satellite application in that there is no way to confugre the application to NOT use LCP. With GPRS, I am always authenticated, so no username and password is required; however the satellite application requires this step - when it doesn't get a response it just disconnects. The mitigation I have found for this is to have the computer where the Direcway application is running "dial" another computer on my LAN and that is already connected to the internet via GPRS. The answering computer gives the Direcway application what it needs in the way of authentication and I am not using land lines but instead GPRS for the outbaound - everyone's happy.

So the final piece of this is getting that dialed-in call (Private PPP WAN) from laptop 2 to talk to the already connected GPRS (Public PPP WAN) on laptop 1.