I have situation in with upnp service stream only on interface with have set Gateway set on it. In my house I receive Internet by wireless, and on my pc i put second lan card to stream to my TV's, but there is a problem, upnp notification service is working only on my WiFi connection not on my Lan segment.
I make some experiments, and if i get link change ip to my Lan segment ip it work so problem is in notification ot Upnp service. In some alternative software, there is option on with interface must work upnp service
Soon I'll test it, but it will be very easy an more informative, to be put as option on configuration. For example "Use on interface [drop down list with interfaces]", it will be usefull, also option "On all interfaces [check box]" also.