I don't believe master will communicate with nodes over wan interface.
Worth trying, you never know, but I won't implement that communication over master wan port. Under the assumption it will go to ISP and that won't make any sense. Plus it may not be secure (I'm yet to capture traffic and see if that traffic is encrypted).
For you this should be an easy one, configure the master while connected on wan port and add a node (that part is over wireless). Move the node where it belongs, wire it on its wan port and check the master if it communicates with node over wire. If not, move the cable from wan to Lan on the master and they will communicate over wire.
Worth trying, you never know, but I won't implement that communication over master wan port. Under the assumption it will go to ISP and that won't make any sense. Plus it may not be secure (I'm yet to capture traffic and see if that traffic is encrypted).
For you this should be an easy one, configure the master while connected on wan port and add a node (that part is over wireless). Move the node where it belongs, wire it on its wan port and check the master if it communicates with node over wire. If not, move the cable from wan to Lan on the master and they will communicate over wire.