Obtaining IP address behind F5

Using Webcenter Portal and trying to call an EL expression to obtain IP of local machine. We sit behind an F5 appliance and IP that comes up is F5 IP. Attempted to update iRule on F5:

when
HTTP_REQUEST {

    HTTP::header insert WL-Proxy-Client-IP [IP::remote_addr]

}

This caused an issue with Weblogic starting up.

The EL I am using: #{facesContext.externalContext.request.remoteAddr}

Does not seem to take parameters, since I would like to call: request.getHeader("X-Forwarded-For")

Anyone have any information related to that?