This is just a warning for anyone trying to connect to their IPspec VPN using Dlink 2750B.  the router firmware is faulty and you will be unable to connect to the VPNs if you are running this DSL wireless router old an older firmware.

I had recently bought D link 2750B modem from Office Works in Sydney, it came with AU_3.02 firmware.  I wasted several hours trying to connect to the VPN through this router, tried different port combinations, DMZ etc however nothing worked. Even tested with older AU 3.01 and newer AU 3.05 firmware.

After running out of options and ruling out that my PC/laptop and the VPN client was at fault, I contacted D-link support and they confirmed that there are issues in the firmware with VPN implementation and provided  a new beta firmware with the fix. I loaded the beta firmware and VPN connection was successful in the 1st attempt.  Hopefully dlink will include the fix in any newer releases (> 3.05) of the 2750B firmware.