Hey Hoolio,
Thanks for your response.
although one of the server is IIS, my problem is about the source code as I cannot change it.
I was trying to assign client ip to LB's local IP when the connection is made from the client to server through LB. I hope that when this is done, the server will see/think that the remote address in https request is client ip rather than LB's IP.
The servers get IP from the LB, but SNAT is opened because the servers start request to outside (e.g. sending mail)
If this can be done without changing any other part of my whole network, i am saved.
-Comex