I have a WiFi network setup with a router (with WiFi) and a WAP (Wireless Access Point). Specifically I use an ASUS-AC66U as router and as WAP I have an ASUS RT-N56U.
As modern devices do, they choose WiFi channels automatically. They automatically choose different channels for the 2.4GHz band.
However, I have noticed something surprising concerning the 5GHz band. They both choose Channel 36. If I reboot one of them, it chooses 36 again after startup.
Normally using the same channel would cause conflicts, reducing the bandwidth. But these two devices seem to choose the same channel on purpose!
Is it so? Do they perform some sort of negotiation at startup and then cooperate in using the same channel? Or is this a bug?
(The negotiation theory is perhaps strengthened by the fact that they are both fairly modern ASUS devices with similar, up to date firmware, 18.104.22.168.374_726 and 22.214.171.124.374_239, respectively)
I have not detected any reduced bandwidth, but it is hard to tell.
Clarification: The WAP has an ethernet cable connection to the router. So if I understand the term correctly I use "ethernet backhaul".