In this article I describe a problem that I ran into when trying to connect more than 50 devices to a single radio (WiFi SSID). I discovered this issue on Tenda AC15 and Tenda AC6 routers. I took the Tenda AC15 out of service and replaced it with the Tenda AC6 as I thought it was a router issue. It wasn't till I started having issues on the second router that I did further investigating.
Issue
I started to have connection issues when connecting to a Wireless access point that was already handling a large number of clients. I was struggling to understand why I was getting what appeared to be random rejections to join a wireless network even thou I have the correct ID/PWD and was able to connect previously.
Understanding The Issue
I started to play with radio channels, bandwidths, security, clearing network caches, routing tables, etc. but nothing was working until I realized thru my testing that while the router with the DHCP table could handle many entries (set to 2-254 IP addresses), that the actual number of "active" clients never exceeded 50 when all WiFi connected to a single radio (in this case the 2.4MHz radio). This triggered me to realize that internally on the Tenda router there likely is a client limitation per radio of ~50 devices. Since I have many (just around 50) IoT devices all on the 2.4MHz radio - mostly light switches, etc., I am likely hitting an internal limit for the radio and this likely is the reason I am not able to join the radio.
I tried the other radio (the 5G radio) and I am able to connect. Therefore, since my IoT devices are all on the 2.4 MHz radio - I am likely hitting some sort of client connection limit for the radio.
Now What
Eureka - this would explain the issue. There appears to be a limit to the number of devices a single radio can service. This of course is likely calculated based on an algorithm that has to take into consideration how much data a device can be expected to transmit/receive. In my case this is very little as I am managing IoT devices.
So what can I do - it appears that I will have to logically divide my network into segments and only allow a limited number of devices on a single radio. The challenge is that the controlling application (in this case the Google Home App) will want to maintain ready access (ideally in the same address space) to all the devices it wants to control.
Testing/Proving the Theory
For now - I am going to reduce the number of devices on the 2.4MHz radio of the router. Moving all the Google assistants, thermostat and chromecast devices to the 5G radio to free up some slots on the 2.4MHz radio. Leaving just the light switches and any other devices that only support 2.4MHz. I also moved the Nest doorbell to "router 6" as it requires 2.4MHz. If my theory is correct, this should free up enough resources (i.e. client connection slots) to allow for new connections to the 2.4MHz radio.
Success
I am now able to consistently and reliably connect to the 2.4MHz radio. What I did was to free up "resources / slots" on the radio by moving off as many devices from the 2.4MHz radio and onto the 5G radio. Eventually this freed up the radio to allow it to accept new connection requests.
I am unable to find information for my Tenda AC6 device that indicates exactly what the limit is for a single radio, but at least for now I know what the issue is and I now know that my Tenda AC15 is also working as designed and can be put back in service. From my research, you should try to limit a radio to a maximum of around 30 devices/clients.
Here is an internet review that claim the AC6 is limited to 20 devices
“The Tenda AC6 takes what’s great about most high-end routers, like beamforming technology, ARM chips, 20 device support, coverage“
This is a key discovery when leveraging WiFi devices and their radios (SSID), especially for folks wanting to use many (>50) IoT devices such as light switches, cameras, video doorbells, Smart thermostats, etc. in the same address space.
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