MS vpn (pptp)

I successfully set up vpn many times following this guide:
SuSE 10.0 PPtP VPN into Windows - openSUSE Forums

But it is not working everytime - sometimes I get completely different ip and different mask, so manually setting up a route will not work properly (/etc/ppp/ip-up.local).
Is it possible to set-up route properly like windows does?
I know there is “default route” settings, but this will bork my current routing setup, I would like it to be just another route, but not my default.

EDIT: no, I don’t want to use networkmanager, since I use my machine as router too.