In Debian, how can I route rtorrent to a certain network interface, say ppp0?

Question

I have purchased a PPTP account from StrongVPN and configured the setup by these (http://pptpclient.sourceforge.net/howto-debian.phtml#configure_by_hand) instructions and now I want to have rtorrent do its communication to the Internet through this VPN tunnel.

So I have a ppp0 interface, which has the VPN tunnel. What is the next step? I guess it has something to do with the routing tables?

I am new to routing, so please be elementary and precise so that I understand!

Thank you!

Answer 1

http://libtorrent.rakshasa.no/rtorrent/rtorrent.1.html

-b a.b.c.d    
Bind listening socket and outgoing connections to this network interface address.