The following line is executed in ip-up before ip-up.local is called:
/etc/sysconfig/network-scripts/ifup-post ifcfg-${LOGDEVICE}
The problem is that ifcfg-ppp0 (or whatever) is not used in kppp and
doesn't exist. Therefore ifup-post exits with nonzero exit code and ip-up
script is aborted. The following may fix that problem:

[ -f /etc/sysconfig/network-scripts/ifcfg-${LOGDEVICE} ] && \
  /etc/sysconfig/network-scripts/ifup-post ifcfg-${LOGDEVICE}