Ok, I have a Windows Server 2008 R2 box on an internal network, running Routing and Remote Access. It's configured to accept PPTP connections.
What I can't figure out is why no one external to the network (tests run inside the network allow the Windows PPTP client to connect successfully) is able to connect. It says that GRE traffic isn't being passed through to the server (Windows VPN client error 806).
I know on the Linksys WRT54G routers, they had a kind of hack that if you forwarded *port* 47 to an internal location, the router would actually understand that it was *IP type* 47 and pass it along as required, allowing that PPTP traffic to go through without issue. What I don't understand is if there is a similar workaround (or if one is needed) for Tomato, or if I'm missing something.
Potentially relevant settings:
TCP+UDP port 1723
TCP+UDP port 47 (tried with this both enabled and not)
Advanced \ Conntrack/Netfilter \ Tracking/NAT Helpers:
GRE/PPTP: checked (tried with this both enabled and not)
Tomato version: "Tomato Firmware RAF1.28.9006 MIPSR2_RAF K26 USB VPN-NOCAT"
Does anyone have any suggestions as to what I can try here?