pfSense

upnp is already multi interface aware afaik. I know it can atleast use multiple LAN connections. Might need to check if it support binding to multiple outside addresses as well.

Just making upnp add rules for both WAN interfaces is doing the simplest thing here, considering you are opening up a port on your router anyhow, it might as well be both.

I just tested pfSense 2.0-RELEASE and with multiple WAN w/ multiple public IP addresses, selecting the LAN interface did not work properly. uPnP only binded to one of my WAN. uPnP does not add proper rules or open ports for multiple WAN interfaces.

There is a MULTIPLE_EXTERNAL_IP option in miniupnpd that allows you to specify multiple external IP addresses, and then map them based on the local client like so:

listening_ip=192.168.0.1/24 x.x.x.100

That maps traffic from 192.168.0.1/24 to the external IP of x.x.x.100.

The dist config seems to suggest that using multiple ext_iface lines will work, and a quick experiment suggests that does work as well, but it doesn't add the mappings to all interfaces, only the last one listed, so it may not be quite that easy.

See also #2743

any odd of this making 2.3 seems other users of miniupnpd claim it works haven't studied the config differences

I am really interested in this feature as i use dual wan and this is a must have in my book as changing wan for UPNP every time my wan fails over

Same, interested, all packages should have multi-wan awareness?