I have a PPTD server (pptpd) running on Debian and my clients are either Windows or Mac OS X machines. I also have an internal DNS hosted at the PPTP server since I want to resolve internal machines.
It runs smoothly all the time, except for a few DNS issues from time to time where the clients cannot resolve any of the internal domains for 10-20 seconds, then all works fine, then it happens again and so on.
The server is always up and a tcpdump 'udp port 53'
never shows anything when I try to 'dig' the internal machines, so I'm not sure how to troubleshoot.