Hi, don't know which version of kppp you are running. Maybe you hit one of the problems discussed in /usr/share/doc/kppp/README.Debian:
kppp and execution of kppp ========================== In order to actually use kppp you must first be a part of the "dip" group. This is the same for using PPP in general on Debian. If you are not a part of this group you will not be able to actually run pppd or setup proper connections. kppp and immediate disconnects ============================== In order for kppp to properly work you must set "noauth" in /etc/ppp/options. Keep in mind that you main have /etc/ppp/options.ttyS0 (For example) so make sure you change it in the proper (all?) file. The default is "auth" so if you don't change this most likely you'll connect and end up just getting a disconnect shortly after. Cheers, Thomas