I mistakenly assumed you had a block of static ips from your ISP. Unnumbered mode only works with a block of static ip addresses ... typically in a business environment.
However, that doesn't mean we still can't figure out how to resolve your problem.
Depending on if you have a single static ip address or your modem receives an ip address via DHCP, you will use a form of tranparent bridging. You will probably need to call Qwest (I know ... an unpleasant experience to say the least) to determine exactly what transparent bridge settings you need. Here's a link for your modem manual: http://www.scribd.com/doc/238259/gt7...ser-manual-v20
. Look towards pages 57-62 or so ... it has the steps for doing transparent bridging. Perhaps you can determine the settings on your own. Good luck ... let me know how it pans out.
***Note*** Keep in mind that if you're trying to establish a vpn tunnel between yourself and a friend ... you're going to struggle at times if your ISP issues your public ip address dynamically. If it keeps changing, you're going to have to reconfigure your vpn routers with the new ip addresses. You'd be better off getting assigned a static ip address (if you haven't already) ... it costs $5 more month I think.