How to preserve client ip address except x-forward for,point server's gateway to seft ip

I think you have to explain all over again. It was not clear enough to help you.

 

Let's me guess

 

 

Client -> F5 -> Server

 

 

You said server can't change ip so there must be server's gateway such as router, L3 switch. and then you put f5 into this system right?

 

 

Anyway, if you can't explain clearly enough in english, you can type thai also.