Proxies like KEMP LoadMaster, TMG (with a plugin), pfSense and others allows us to give the client's IP to the destination Real Server by inserting an additional HTTP header (called X-Forwarded-For) when L7 is used with non-transparency.

This option of inserting the HTTP header (called X-Forwarded-For) allows the client source IP address to be logged by the Real Server's IIS logs.

My idea is that SmartTrack use this method to catch the real client IP Address and use in Who's On feature.

Something like:

var forwardedFor = Request.ServerVariables["HTTP_X_FORWARDED_FOR"];

var userIpAddress = String.IsNullOrWhiteSpace(forwardedFor) ?
    Request.ServerVariables["REMOTE_ADDR"] : forwardedFor.Split(',').Select(s => s.Trim()).First();