I've done something very simple. Or so I thought...
I have setup VPN client access in TMG (or ISA, they're pretty alike). I created a group called VPN in AD, added that as allowed VPN users in TMG, setup a IP scope for VPN clients (192.168.6.0-192.168.6.255) and added network rules routing between VPN Clients and the Internal network on TMG (192.168.5.0-192.168.5.255). I also added an Allow all rule between VPN Clients and the Internal network in firewall policies.
To my problem: I connected to this network from a client running Windows 7 using PPTP connection (which is also set in TMG). I am able to login without errors, but when I try to contact any server on the Internal network, I get no response. So naturally I did a lot of troubleshooting (there was nothing showing up in the logs on TMG, no Denied Access anywhere) without success..
Later, I tried connecting the VPN using my mobile phone, and used a RDP client on my phone to contact a server on the Internal network. That worked!
I tried another Windows 7 workstation at another physical location, and using that I could not even login to the VPN.
Yet another workstation at another physical location, and I can login AND access the Internal network.
What could be causing these discrepancies? Why would it work from some places, but not from others, and with different errors?
Thanks in advance!