Is it possible to replace source ip as x forwarded ip?

Draco,

Here is an iRule that should take the contents of the X-Forwarded-For header and SNAT to that IP. I would be careful with this though as unless the F5 is set you be your default gateway, the server may try to send the data back to the client directly. This asymmetrical routing will cause issues with connection.

when HTTP_REQUEST
{
    snat [HTTP::header value X-Forwarded-For]
}

If you have any issues with this iRule or any further questions, I am sure I can help.