[skipped]
> | > >Couldn't set interface address: Address 89.178.99.0 already exists
> | > >local  IP address 89.178.99.0
> | > >remote IP address 195.14.40.9
> | > >primary   DNS address 195.14.50.1
[skipped]
> I don't know. I have not used pptp before. It could be that pptp configures
> the network interface and pppd tries to do it again.

I have avsolutely the same problem under netbsd-3.
/etc/ppp/options is empty.
/etc/ppp/peers/vpn:
debug
kdebug 7
name cheusov
pty "/usr/pkg/sbin/pptp 217.21.51.32 --nolaunchpppd"

pkgsrc versions of pppd(2.4.3nb1) and pptp(1.7.0nb2)
DOES work under Linux and doesn't under netbsd-3.

Do either pppd or pptp have linux-specific code?
Can anybody with knowledge of ioctl's and blah-blah-blah
check this?

P.S.
About MESSAGES:
"If you experience problems with this package, try rebuilding your kernel
without the 'gre' pseudo-device."

1) OpenBSD has sysctl net.inet.gre.allow
What about adding something similar to NetBSD?
2) MESSAGES do not tell in what cases netbsd kernel should be recompiled.
mppe only or whatever else?

-- 
Best regards, Aleksey Cheusov.