I just recently set up the VPN for my network and did PPTP passthrough on the router and forwarded a couple of ports that seem to be VPN specific 1723 TCP/UDP and 4500 UDP. However the VPN was not working it was telling me that I don’t have the ability to send and receive GRE packets. For testing purposes I checked the option to forward all TCP and UDP traffic to my Windows SBS 2003 box. Now the VPN works fine. What ports should I be forwarding, because obviously I don’t want to forward all traffic to my SBS machine. I looked at a Microsoft Technet article about which ports to forward depending on the situation and the ports it told me to forward weren’t the right ones.
