ac87 concurent client limit?

[strumf666]

Update: After changing the channel for 2.4GHz, RPi's are not dropping from network anymore, even though I am back on the same channel as before... Seems like the router needed to have the settings "refreshed"?
Sadly, that's not the case for 5GHz... Also 5GHz is weird as @Sky noticed from the picture, even when I have channel bandwidth set to 80MHz it is acting as if it were set to less. I did some testing with speedtest in browser on a laptop and I am getting a slightly higher speed if I am connected to 2.4GHz than on 5GHz with the laptop sitting next to the router.

 

[Morphy99]

Hi @strumf666 I'm having a similar issue with a RPi 4 B connected to 5Ghz from a RT-AC87U so I'm glad I'm not the only one! I wonder if we can work together to find out the culprit here First off we need to establish if we're having the exact same issue.

A few questions:

1. Which OS do you have on your RPi's?
2. Are they all RPi 3 with built in wifi?
3. When the issue occurs does restarting the RPi resolve the issue? - This is different to me, I have noticed that occasionally it will reconnect after keep trying (I have a script set up to do this) but usually restarting the RPi does not make it reconnect.
4. Do all of your RPi's suffer this at the same time? I had only one connected to 5Ghz however now I have put in another to see if this is affected as well. Last night I had the issue and it seemed to affect both devices at the same time.
5. Which channel is your 5Ghz on and what bandwidth? I have tried different channels but it would still be interesting to see.

Well this exact same setup worked without problems for a couple of years, and at the time when problems began I didn't upgrade or change anything, so I am a bit puzzled...

This is troubling as I would put this down to a setting or software problem, not hardware failure but can you verify if the router has been updated or the RPi at all during those 2 years? From what I can see with my issue, it will not occur straight away but sometimes after a few days or even hours.

I'm a bit alarmed at your router being damaged by lightening! I have first hand experience of this when I used to live in the hills in Spain! My router is second hand from Ebay and I've only had it a few months so I'm not sure if electrical surge damage is an issue, I find it unlikely here in the UK though.

 

[strumf666]

Hi,

1. Volumio.
2. Yes.
3. Not for long and it got worse with time, at first a restart was good for a couple of days at least, later on, for a few hours at most and occasionally rpis would drop from wifi during music playback (usually it happened when they were idle).
4. Yes, I had issues on both 5GHz and 2.4GHz and only after I changed channels back and forth on 2.4 GHz the issue disappeared; strangely enough this didn't help at all with 5GHz.
5. Bandwidth is set to 80MHz, but it doesn't look it works at 80MHz. I tried different channels to no effect.
Router and RPis are regularly updated.

Yes, that was a bit unfortunate as it killed the WAN port on the router. Killed the modem as well, but ISP replaced it since its their property. I got fibre since, so this can't happen any more (surge through the telephone/internet line).

 

[Morphy99]

Hi,

3. Not for long and it got worse with time, at first a restart was good for a couple of days at least, later on, for a few hours at most and occasionally rpis would drop from wifi during music playback (usually it happened when they were idle).

I think this might be a different issue to mine but it could be related. My RPi's all stop connecting to 5Ghz at the same time, so it's something router related. Strangely they connect ok to 2.4Ghz when the 5Ghz is down. Also no other devices seem to suffer with this. I'm running Libreelec not Volumio which have some Kernel and OS differences. I've set up another RPi with Raspberry Pi OS so will be interesting to see how that behaves.

 

[Morphy99]

A quick update, the pi with RPi OS lost connection at the same time as the others so I've eliminated it being an OS issue. I've been doing some more monitoring with the wifi and noticed other devices can disconnect quite often and although they associate again this may be part of the problem. This was also happening on 2.4 as well as 5Ghz.

I've done some reading around others with issues on here and found some discussion around the Group Key Rotation Interval. I've tried disabling this (0) for the time being to see if it improves things and I've noticed an improvement on the 2.4Ghz devices at least. I've read conflicting reports to the security risks of disabling it. One user suggested setting it to the same as the DHCP lease, others to 1592000 (max).

I've also noticed the temps of my router are a little high but still within tolerances apparently. Currently running around these:
2.4 Ghz: 47 °C; 5 Ghz: 69 °C; CPU: 78 °C
If I still keep having issues I'll look at installing some active cooling on it.

At the moment I've got 5 days up time and no issues so far!

 

[Morphy99]

UPDATE: Today I had the issue after just 3 days up-time and active cooling with the key rotation disabled
I've disabled all beamforming features now. Beginning to think this is just an issue with the router that I can't resolve with settings

 

[Sky]

Domain666/5G are my SSIDs.; Domain665 too, but thats another router in the basement so not important in this case.
RPi's are b/g/n/ac, before this issue I had them on 5GHz, and I plan to return them to 5GHz if possible.
Thanks for the explanation; I wasn't aware of prime channels, I thought they were all equal.
In the above pictures I had set the 2.4 to N only and 40MHz, in this picture I changed control channel to 3; bigger picture attached, hope you can see it better.
For 5GHz I had set the bandwidth to 80MHz in the picture above.
View attachment 26918

[Fyi, the small pictures are fine. Clicking on them magnifies them nicely.]

In your October post your signal is quite degraded from before, sitting at about -63db. At this strength you may be getting interference from AMIS, A-1, & Irena. It also appears you are set to ch5 vs. ch6. If you're going to be that close in signal strength, being on a "play nicely" channel becomes even more important. You prior pic showed a good signal at about -55db.

Personally, I also have had success by locking-out some devices that have multiple abilities, i.e., b/g/n/ac, so they can are limited to the process I want them in. For instance I had some issues with some cameras that did well on 2.4 but poorly on 5 due to their distance & position from the router. Blacklisting them by MAC from the 5GHz band did the trick and they work perfectly now.

To do this on the left menu go to Wireless > [Wireless MAC Filter] >

select the band you do not want the device to use​

Enable MAC Filter (yes)​

MAC Filter Mode (reject)​

select the MAC from the client name list > click add > click apply.​

 

[strumf666]

Bought another router to use as an AP, not problems since.

 

[Morphy99]

Bought another router to use as an AP, not problems since.

To be honest it seems like the easiest option. I'm about this close to doing the same. I've hard wired the pi I was having problems with but I still occasionally have issues with devices dropping off the network on 2.4. The thing that's bugging me the most now is DHCP. If I add a new device to the WiFi it picks up an address from the pool but then I like to assign static DHCP addresses to them after that. Sometimes, if I save this on the router then reconnect the device the router will still give it the old address. Nothing I do will make it change apart from restarting the router. Yesterday on top of this the router gave a new device the same host name as a device already on my network, that confused the hell outta me for about ten minutes! Why would it do that!

Honestly never buying Asus again. I'm going to try one more go resetting to defaults and all the tips around this. Then if that doesn't work back to stock. After that it's going in the bin.

 

[Morphy99]

In your October post your signal is quite degraded from before, sitting at about -63db. At this strength you may be getting interference from AMIS, A-1, & Irena. It also appears you are set to ch5 vs. ch6. If you're going to be that close in signal strength, being on a "play nicely" channel becomes even more important. You prior pic showed a good signal at about -55db.

-63db is not degraded, packet loss shouldn't occur until at least -70db

 

[KsWoodsMan]

Domain666/5G are my SSIDs.; Domain665 too, but thats another router in the basement so not important in this case.
RPi's are b/g/n/ac, before this issue I had them on 5GHz, and I plan to return them to 5GHz if possible.
Thanks for the explanation; I wasn't aware of prime channels, I thought they were all equal.
In the above pictures I had set the 2.4 to N only and 40MHz, in this picture I changed control channel to 3; bigger picture attached, hope you can see it better.
For 5GHz I had set the bandwidth to 80MHz in the picture above.
View attachment 26918

While sticking to the 3 channel rule/guidline , I've always found best range and preformace when using a control channel that matched the weakest station with the least congestion and overlap.
When 2 stations are on the same control channel they will try to co-exist and have better luck doing so this way as opposed to using the next channel
The "neighbors" you have showing appear to be using channels 1, 6 & 11.
Good for them. Knowingly, or not, they are being good wifi neighbors.

By using an overlapping adjacent channel or one between what they are using, their signals appear as noise on your network.
It's not on the same control channel so there is NO cooperation between the stations or access points.

A good analogy is to tune an AM/FM radio to your local AM station.
Then tune the dial to the next channel/station either 10KHz up or down (one click or tap on a digital tuner).
You can still hear that station, though it isn't as clear and might be covering the weaker station from another area.
Go one more or 20 KHz off from the center of that local station.
Can you make out anything from either the station ON that channel or the strong one in your area ? probably not, or not reliably.

When using the same control channel as the weakest one available you can both send and receive between each others "gaps".
When one station is using the very next available frequency/channel BOTH stations cause interference with each other causing disconnects from the clients also getting this interference..

2.4GHz WiFi should only really be considered to have 3 channels. The 3 (20MHz slices) that don't overlap or cause inteference. 1,6 & 11.
By using different control channels from your neighbors, on overlapping channels, you are getting AND causing interference.

By having 20MHZ neighbors on 1 & 6, when you set yours to control channel 3 you are getting AND causing interference with no cooperation.