Tested this over the weekend. (a) Setup as per Figure-3 DECO M5 (UNIT 1) (MAIN DECO) went crazy, from the switch, lights were blinking non-stop. Think it created a loop of sorts. DECO's light also...

Now this gets interesting I sent in a support ticket before posting here on the forums and the official TP-Link response is as follows: *Note: I provided them with the same layout etc....

Thank you!

Thank you. But is there a means of verifying that the DECO's are using the ethernet as the backhaul?

My environment using ASCII art |-------------> DECO M5 (UNIT 3) | WWW ---> MODEM ---> ROUTER ---> SWITCH -------> DECO M5 (UNIT 1) (MAIN DECO) | |------------> DECO M5 (UNIT 2) (a) MODEM is supplied...