Hi Vincent,
you're right this is my case, controller behind a firewall and AP behind a ISP modem. in addition necessary configuration are done at the firewall level, i mean static nat from outside to inside with port forwarding UDP 4500&w.
Yes, i try to use this my AP as a remote AP (RAP).
for paquet capture (using wireshard) i noted tahat AP doesn't generate any traffic even his network card eth0 well configuration with LAN and master IP.
Note : AP reboot a lot see the txt of the reboot sequence (I replaced controller IP with X.X.X.X in txt file)
Thanks, waiting to hear back from you.