As I was deperatedly trying to setup a VPN server with relatively easy acces on windows machines, I always use PPTP server for it.
But I couldn't get it running at first.
I use Webmin to set up the server, setting up pptp is not very hard, but on sheevaplug (with my kernel 18.104.22.168) you run into issues:
> apt-get install pptpd ppp
I believe it automatically defaults to MPPE auth. But you need to disable this!
Since: MPPE requires support in both the PPP daemon and operating system kernel. --> we dont have it
Second is we are still coping with this bug:https://bugs.launchpad.net/ubuntu/jaunty/+source/pptpd/+bug/352622
Commenting #logwtmp in /etc/pptpd.conf did the trick, as described.
Now, pptp VPN is working!
I also had the issue that pppd wasn't executable, but think a re-isntall fixed it. Check it if it is still not working?