connect the sspr v4.5 after a proxy and receive the ip address of the client ?

how can i connect the sspr v4.5 after a proxy and receive the ip address of the client in my intruder message after a bad login i can see its ID but i receive the address of the proxy. the variable that saves the ip of the client is X-MCDN-REMOTE-ADDR how can i set the SSPR to use this variable for the client address