Only one PPTP session is allowed only by TMG…if the second user tries to initiates its outbound VPN connection…it would fail.
Cause and Analysis:
– From the Network package captured on TMG, the Client caller ID was changed by external router device and thus the connection was discontinued. – Research and found this issue might be related to the below article: http://blogs.technet.com/b/isablog/archive/2009/01/07/a-pptp-client-might-fail-to-connect-to-a-vpn-server-on-the-internet-through-an-isa-server-2006.aspx – Changing the External Gateway device to Cisco 857w to have a try, and we find everything works fine now.
To solve the issue, we need to contact the router vendor to check if a firmware update exists that fixes the issue or even change the router vender to another one like Cisco 857w.
Please close this case because prior to deploying the Cisco 857W router, only one user is allowed to VPN to Southern Africa VPN server. After the Cisco 857w was deployed, TMG was able to service two simultaneous VPN sessions from the LAN to External.
Thanks again Magwinya Wired Support!