dial on demand router for analog

Hello

My problem is that I'm trying to make an absolutely dau-proof router, so I copied the entire folder on hd, made a chroot and am now trying to set the hd-running knoppix as a complete router for dial on demand via analog modem before I'll later make an image of it and have a preconfigured cd-router.
But the thing is, I simply can't get the pppd to run with the demand-option. It always says that the daemon died of uncompatible options, whenever I activate it.
Now in the man pages it says something about dial on demand having trouble with dynamic IPs, because it needs to know the ISP-IP beforehand. But surely there is a way to use this with the normal dynamic-IP-ISPs, is there? Or is there some other problem that I just didn't see?
and where in this whole mix do I need to worry about wvdial, which I'm currently using to invoke the pppd?
I really hope that someone can help me with this mess, be it by posting a link or giving a short explanation.
Thanks a lot already ^_^;;