After 
fiddling for hours with a 7100 AP to discover that it does not want to work together with my Linksys router, I decided to give up for now. I suspect that it just doesn’t like retrieving an IP address from the router.
Talking about that router, initially I wasn’t happy with it, but after applying the latest firmware upgrade (January’s one, I don’t see a reason to upgrade to the June one) it has been running steadily. Compare that with D-Link: the last time there was a 7100 firmware upgrade was years ago.
There might be a chance that one day OpenWRT will support that D-Link one. For now, back to the 11 MBs AP.