source: https://www.securityfocus.com/bid/1049/info

By default, Real Server includes the IP address of the server in data sent to the client. If the Real Server is installed on a machine in a NAT environment, (where requests from the outside network are handled by reverse proxy), this will reveal what are supposed to be private, hidden IP addresses.

$ GET http://realg2.example.com:8080/ramgen/foo.rm
reveals-
rtsp://192.168.11.12:554/foo.rm
--stop--
pnm://192.168.11.12:7070/foo.rm
server info:
WinNT Version 6.0.3.303