Can't Access Main Or Guest Network on 2.4GHz Band of Satellite Connected By Ethernet-Backhaul
I've noticed that under specific circumstances, clients can't connect to the 2.4GHz band on one of my satellites (the one connected by ethernet-backhaul).
I have four Deco M9Plus v2.0 running firmware 1.5.6 Build 20211018 Rel. 35617 in Access Point mode. Two of the satellites are connected using WiFi and directly connect to the main Deco, one is connected using ethernet-backhaul, so it's a star network.
Usually Completely Normal Connectivity on All Disks
If I bring the network up one disk at a time: main disk first, then WiFi-connected satellites, then ethernet-backhaul connected satellite, everything works fine. Clients can connect on both the 2.4GHz network and the 5GHz network on all disks.
If I use "Reboot All" or if there is a Power Failure
When the ethernet-backhaul connected satellite is online at the time of the reboot, then clients will not be able to join the 2.4GHz network on that just that disk. The same clients can join at any of the other three disks, but receive an "Incorrect Password" response from that disk. 5.0GHz clients can join perfectly well everywhere.
On the ethernet-backhaul connected satellite, the 2.4GHz SSID is being broadcast (confirmed using inSSIDer and showing up in the list of available networks for the 2.4GHz-only clients). The same client can be transported to within range of the Wifi-backhaul disks and will connect fine, so it isn't a client problem
It looks like the configuration of the ethernet-backhaul connected satellite containing the passwords - which I assume is downloaded at boot-time from the main Deco - is invalid if it is online at the time the main Deco boots. It works fine if introduced into the network the other disks have settled down.
I've also tried a Deco M5 running firmware 1.6.0-220525 as the satellite and it shows exactly the same behaviour, so I would assert it's a firmware bug in the main Deco and not in the satellite.
I haven't tried updating the disks to the 1.6.0-220720 beta. The inconvenience of having to run around the house to reboot the disks in the right order is less than that of testing beta firmware.
The easiest way to reproduce the problem is to configure the guest network to be 2.4GHz only. You can then easily see a client such as an iPhone being able to join the guest network in the situation where the there ethernet-backhaul connected satellite is brought up in order (last), and gets an "Incorrect Password" response after a "Reboot All". The same iPhone will always be able to join the network at the main Deco on the guest network.