L2TP, despite its name, is typically used in L3 mode (IP tunnel), and so it is in your case. So the explanation and advice what to do is here (unlike with IPsec, I am sure the advice will work).
L2TP, despite its name, is typically used in L3 mode (IP tunnel), and so it is in your case. So the explanation and advice what to do is here (unlike with IPsec, I am sure the advice will work).