Vermillion

Hello! Myself and a friend would like to connect to each other for a IP game, but the problem is we're both on shared networks - that is, we're both on a network locally that has multiple computers sharing one external IP address. This seems to cause problems detecting each other - we can try to connect to one another's external IP but CM fails to detect. I was hoping there was a workaround or that I'm being stupid about something. Thanks for any help!