Trying to establish a PPTP VPN connection between SBS 2003/ISA 2004 and various Windows XP, Vista and Windows 7 clients.
Everything was good and fine until the old D-Link Router (DI-624) finally gave up working. Trying to set up the same thing on the DIR-855 replacement seems to be a major ordeal with little solutions available. At the same time it is hard to believe that this hasn't been done. The DIR-855 has the latest firmware, 1.21 NA (beta build 07). Tried all builds since 1.10 with no difference, hardware is A2.
Windows VPN software comes back with error 720, not being able to negotiate the appropriate protocols upon conection (able to connect, verifies id/pw ok, stalls upon final verification).
All points torwards (ultimately a guess though) the GRE protocol not being set up properly (which I can't, like in DI-624 just have as a firewall rule).....
Right now I've set up Virtual Servers for PPTP (1723/1723) TCP/6 and GRE (grayed out/grayed out) Both/47.
I seem to be missing something big-time. Anyone having any wisdom on this? How can I set up GRE properly and verify that this is/is not the issue?
Thanks a buch in advance.