Why would it not allow this? Read the article I linked, it explains why double Nat is not really different. A specific Nat setup would be my home connection, o

Why would it not allow this? Read the article I linked, it explains why double Nat is not really different. A specific Nat setup would be my home connection, or pretty much anyone using the same ISP. It's CGN and then another Nat at home. Stun works fine with that.