I've configured a VPN on a Windows 2003 server and forwarded port 1723 using the linksys RVL200. There is no option on this router to forward the GRE protocol but PPTP passthrough is enabled.
The VPN hangs on 'verifying user name and password.' I'm pretty sure this is because the router is not passing GRE. I read that this was a problem with older firmware versions but I'm running 1.1.7 which is the current, and only, version available.
I've compared the VPN configuration with other known-good configurations and I'm confident it's not an issue with the VPN configuration. I believe it's an issue with the PPTP passthrough not really working.
Does anyone have any suggestions?