We just started implementing L2TP VPN connections into a Windows 2008 Server and it work superbly. After successfully getting my test environment up and going we started rolling them out in production server and shipping out to clients. We currently have 85 VPN connections and the Windows VPN connections have no issues keeping there IP's when they disconnect. After about a week the issue started to rear its ugly head and I started noticing the IP's we statically assign the Mikrotik routers (various models) will revert to the small DHCP range I have in RAS. Seems like the Mikrotik's keep the static IP for a couple of days and then pow, DHCP. I kick the routers of the VPN and they call back in like good little soldiers with there static but during the time they are off we loose out video feeds and are at risk of clients getting property stolen. My gut tells me theirs a way to tell the router its static IP is x.x.x.x so it will not loose it but I am unable to find it in winbox, if it was a windows issue I would think I might see the same issue; however the adapters are assigned the IP address. I have noticed this on PPTP and SSTP as well :(