This is what the firewall rule looks like in the RouterOS CLI:-
;;; sn-test-01_auto
chain=dstnat action=dst-nat to-addresses=10.0.0.31 to-ports=12101-12120 protocol=udp in-interface=1_BT_ADSL
src-port="" dst-port=12101-12150 log=no log-prefix=""
And this is what it looks like in the GUI where I set that one:-
@moderators Suggest moving this topic to Routers for advanced setups