Difference between "True client ip" and "X-Forwarded for"

Hello,

Actually the XFF header is inserted exactly for that purpose... to let the backend server knows the "real client IP addr".

Indead, when you have a reverse proxy between your client and server. The reverse proxy most of the time (for simplicity) change the source client IP (this is what we call SNAT is F5 references). So in order to let the server know who is behind the reverse proxy, the F5 can insert the XFF header with the client addr.

In that manner, once the request is forwarded to the client it can process this info.

Hope it clarifies.

Regards