We have a 2008 R2 server running RRAS and we then have an SBS server sitting behind the server operating as the VPN server, in RRAS I can forward port 1723 to the server onsite but cannot forward GRE which could be the reason why our VPN's will not complete.
We get the credentials prompt but VPN will not complete, it errors out.
Can we forward GRE through the RRAS server, there is not the option to forward a protocol only services?
GRE is not a port, so it cannot be forwarded. GRE is a protocol, just like TCP or UDP. Your encrypted packets with PPTP have a modified GRE header, so it anything in the path blocks GRE, no VPN data will be transmitted.
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