After updating several computers of different age (Lenovo Laptop, Shuttle
desktop, self build desktop) to openSUSE Leap 42.1 (kernel 4.1.15-8-default)
from 13.2 I had no connectivity via pptp VPN any longer. Turning off
SUSEfirewall2 resolved the case but is obviously no option. Checks on
networkmanager errors and research via google showed that apparently module
nf_conntrack_pptp needs to be loaded via modprobe to get things running.
The solution I found on the internet was as well proposed by Aeneas Jai�le in
bug 927191 for asimilar problem:

 Can you load the nf_conntrack_pptp module manually and test afterwards?
    ~ # modprobe nf_conntrack_pptp


If it works, you can make loading persistent by
    ~ # echo nf_conntrack_pptp > /etc/modules-load.d/pptp.conf

I didn't validate solution proposed in bug 930896 which looked "fitting" as
well