Billy brother answer
Excuse
me , Twice NAT and Bidirectional NAT (Bidirectional NAT) , are they the same thing?
It is not the same concept. The former usually refers to the simultaneous NAT translation of the source and destination addresses (for example, the source is converted to A, and the destination is converted to B); the latter refers to a source NAT (such as A to B), at the same time, if there is B accessing the client from the server side, it can also be converted to A through the destination NAT, which is common in Static NAT
The descriptions of articles on the Internet are rather messy, and many of them refer to the simultaneous conversion of source and destination addresses as bidirectional nat.
So a simple understanding is that one describes the direction, the other describes the number of NATs, and the same session