I have the Routing and Remote Access service running to serve PPTP VPN connections for clients and suddenly the service stop working. The clients couldnt even give a telnet at 1723 port when testing. Looking for errors in he event viewer, the only thing was a warning message that appeared randomly. The event was from source RemoteAccess and ID 20192:
A certificate could not be found. Connections that use the L2TP protocol over IPSec require the installation of a machine certificate, also known as a computer certificate. No L2TP calls will be accepted.
The service was still running, but when I looked at opened port using netstat, the 1723 wasnt listening, even with the service started and responding to stop/start commands.
I restarted the service and there was no change. Based on the warning message, I opened the Remote Access snap-in and set the number of ports for the L2TP protocol to zero. Restarted the service again and everything went back to normal.
What could cause this behavior if nothing was changed? No patches to the OS, no program installations, no configuration changed, etc. The OS is MS Windows 2003 Standard Server with SP2 running on 32 bits. There was no hardware problem, like disk space or low memory by the time the event started.