House with wifi router in the living room and the signal does not reach the last room. We put a router with openwrt firmware configured as a router, not as a repeater, and connect it to the main router via wireless, so the WAN will be wireless. Now we create our own wifi network with different SSID and different key.
Up to here everything is perfect, but if I turn off or change the main router, the Wi-Fi network created in the secondary router disappears completely because it has no connection to the main router, it disappears !!!
Consequence ... there is no access to the router via wireless, only via ethernet cable and this makes maintenance very difficult. The most curious thing is that if you access via cable and disable the client connection that provides the connection to the main router (which is not operational at this time), the wifi network automatically appears again.
I believe that when you set up a Wi-Fi network in the secondary router, it should never disappear until it was removed, so that the routers could be configured via wireless without needing to establish the cable connection, even if connection to main router is lost.
That's not a bug, but a functional limitation whenever you share one radio for a STA and AP interface. The problem here is that the STA (client- or wwan) interface needs to be brought up first, as that's the one deciding on the channel selection and other basic parameters of the physical radio operations. This means the AP interface can only be brought up later - or never, if the STA interface fails to connect.
This can be avoided by using a dedicated radio for the uplink - and partially mitigated by using travelmate.
Is that functional limitation made on purpose? Because it does not make sense. Imagine that you want to leave several routers preconfigured or that your ISP changes your router. It also does not suppose a security hole greater than if it had connection with the main router. My solution for the preconfigured routers, is to leave the client connection (STA) disabled, then I reparameterize it and activate it. I need someone to explain to me why the firmware has been compiled so that it has this absurd behavior.
A single radio can only operate on a single channel. That you can have multiple "connections" on the same radio doesn't change the channel, just the packets sent over that single channel. If you're declaring that the radio must (or may later) connect to another AP, then it is the channel of that remote radio that determines the channel.
That makes sense, so I'll keep it in mind for my routers preconfigured with the client connection (STA) disabled. It is the only way I have found to access via wifi to routers with this kind of configuration.