I have three clients on my location, two running XP and one running Vista. All of them should periodically connect to central office via PPTP VPN. Until recently there were no problems, but now Vista is suddenly unable to connect any more.
I am getting error 806: The VPN connection between your computer and the VPN server could not be completed. The most command cause for this failure is that at least one Internet device (for example a firewall or a router) between your computer and the VPN server is not configured to allow GRE protocol packets.
I have checked the router (Zyxel Zywall 35) it has both port 1723 and GRE protocol 47 configured OK. Otherwise I would have problems with XP clients, too. Or is GRE important only for Vista?
I havent changed anything - the connection was just lost one morning and I am trying to get it back since then without success. I have tried Microsoft KB 926170 and 929857 instructions, since the error first manifested as 721, but no solution so far.
All clients are on domain, but the domain server is on the host that is available only throught VPN - I guess this might be the problem...