I was having issues connecting both win7 and win10 clients when behind a NAT.  I have confirmed that the native L2TP/IPSec windows supplicant will work after applying the following registry edit, found here.   HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\PolicyAgent\ New DWORD (32-bit) Value:AssumeUDPEncapsulationContextOnSendRule Set the value to 2 Reboot and retest, you should be good to go!  ... View more