enabling UPNP please help

Please help me enabling UPNP on my RB3011. If possible in Webfig or Winbox.

I need it for my server and torrent client. Port forwarding is another and possibly safer option, but I like to learn this UPNP first.

So far I found IP UPNP and all 3 options are enabled now.

Trouble begins with setting the internal and external interfaces. What are they and what do they need to be set to? ether 1 to 10, ether2-master, ether6-master an bridge.
Why are there 2 masters? Or should bridge be set to internal or external? The RB3011 is in Router mode on OS 6.38.1

Will someone please enlighten me?

Internal is LAN, local network where your own devices are connected, in your case probably bridge. External is WAN, i.e. connection to internet. It can be ether1, some pppoe interface, … depends on what you use.

https://m.youtube.com/watch?v=kkeu2t_6O2c