Erratic behaviour of Mango (loss of wifi, timeouts and so on)

Routers
1

Gentlemen, good morning.

I have a home network comprising a Fritzbox 7590 (the "source" of my internet connection) with its own wifi and wifi channel and a few devices connected on the LAN ports.
From one of these LAN ports, I have a tiny switch where I have connected two mango and one Beryl AX.
The cable from the switch is connected to the devices' WAN port, and their "local" IP is fixed and outside of the Fritz DHCP range.
Each device outputs its own wifi, and each wifi is configured with its own channel and SSID to avoid conflict.
To keep wiring neat, all of those devices are within 10 cm of each other.

immagine
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The two Mango have just one client and provide a different VPN to such client.
The Beryl is just used for the adguard filter and occasionally for vpn.
This is why 3 devices. each one performs (well, should perform) one function only so no mess or errors should happen.

What is happening is that, pretty often, parts of this contraption stops responding, with Mangos being more prone to fail than the Beryl.
It looks like the Mango's wifi disappears or , if it's there, no traffic can pass, to the point that it's impossible to load the admin access page (with timeout or partial load).
If i leave open the "overview" page on all devices, i see often "holes" in the status graph, and when it happens i get timeout warnings (the usual "check network environment or reboot).

Local network-wise, the configuration of the devices is stock, apart for the local IP that is fixed on both devices and fritz to avoid conficts.

The funny part is that sometimes everything works like a charm for days, and some days there is no damned way to have it working, even plugging all power supplies off and rebooting all together.

I have the feeling that for some reason some of the device go nuts and starts polluting the wireless environment to the point that nothng works anymore, but i cant' understand why the "full reboot" does not solve anything as well as why some days everything works.

I live in an apartment and the wireless is quite crowded, but i suppose this is quite a normal condition nowadays

So far I tried the most obvious things , such as checking lan cables and checking power supplies... but i have no clues on how to improve this situation.
It may be useful to note that until a few ways ago all the mango were on 3.x firmware, and i've updated to 4.3.18 . Beryl is updated to 4.7. Same behaviour with both firmwares.

anyone is experiencing disruption of this kind? Any ideas for a solution?

thak you .
E.

2

Generally I assume the Mango1, 2, Beryl 1 and Fritz are not the same subnet, right?

So they are supposed to be not IP conflict occurs.

Is it possible to test them one by one separately?

For example, take out Mango 1 separately, connect Mango's WAN port to ISP/Fritz router's LAN port, and see if Mango will work normally.

4

Good morning, Bruce, and thank you for your feedback.

All devices are on the same subnet (10.0.0.x) which is the LAN address pool for the whole home.

Each device has its own ip which is static inside of the lan (say, 10.0.0.1 for the fritz, 10.0.0.2 for the mango1 , 10.0.0.3 form mango2 , .4 for beryl, .5 for my tv , .6 for raspberry and so forth.)

There is a dhcp pool , and all fixed IPs are of course outside of this pool.

None of the gl.inet devices is used as a server for outside world, so there are no NAT or open ports that may cause issues, i guess.

In this sense i suppose there are no conflicts.

Each gl.inet generates a wifi with a dedicated SSID and the IP range of this wifi is different from the LAN (lan is 10.0.0.x while wifi is 192.168.8.x which is default). The wifi serves just two clients.

I hope this clarify the setup. I feel that there should be no conflicts.

Concerning the test of single devices, i have erratic behaviour even with one device .

Originally I have been using only one mango, switching its configuration according to my needs but the configuration change led to massive crashes (i was switching between a openvpn and a wireguard vpn and turning on / off the client device).
I decided to go for dedicated devices in order to avoid the change in setup and in order to leave clients on.
The beryl is "just" an add-on because i like the adguard.

Hope this helps you to help me.
Thank you.
E.

5

Looks strange.

Can SSH to the router via cable LAN with the PC when the issue occurs?

If can, please export the issue syslog and send to me via PM.

6

Hello, Bruce.

Ok, I will try to.
I assume the ssh password is the same as the management interface, is it?
How do I proceed with exporting the Syslog?
I suppose files are somewhere like /var/log/syslog and that doing a cat for the filename while logging the terminal output would work, but I'm not into Linux enough, so I ask.

thank you and have a nice weekend.
E.

7

Yes.

logread > /tmp/logread/system.log
dmesg > /tmp/logread/kernel.log

Then export system.log and kernel.log with WinSCP.

8

Hi, Burce.

I will do, im currently away from home, but i will try to get files as soon as i come back.

Thank you.
E.

9

This might be a very problematic setup.
Wifi transmission typically is up to 20dBm (100mWatt), while a reception of a signal above -30dBm (1 µWatt) will saturate the receiver for the whole frequency band.

We use to be at least 30cm away from the AP with client devices. And with the size of the 2.4GHz and the smaller 5 GHz antenna , the received signal at the client device is expected to be -30dBm and -36dBm. The battery powered client device only transmits at 12dBm or even less for a smartphone (to not heat up your brain).

Setting 2 or more AP's with TXpower of 20dBm at that 30cm distance will probably saturate the receiver (totally distorting the wifi signal for the whole band, so even if using different channels).

10 cm is very very close (15 cm is the safe distance for your body parts)

For AP's I'll recommend 1.5 meter distance between them. Actually you can see the signal strength received, in the operator interface. Good value is between -40dBm and -70dBm.

Some people killed my wifi infrastructure last summer , by using GL.inet travel routers which they put just next to the host AP. ("Hey the wifi speed is not good , lets get closer to the AP"). They ended up by having no wifi at all through their GL.inet routers.

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10

Hello, thank you for your insight.
I tought about interference, and I set power to minimum already.
Note however that before I put up the setup I described I had only one mango and still had issues.

I can't understand what happenes because when it's working... It works even for days without issues. Then, suddenly stops.

Now I'm not home, when I will be back in the coming weeks I'll try to capture logs. We will see.

Thank you.E.

11

There are many possible causes, and receiver saturation is just one of them.
that's the problem with troubleshooting if there are multiple reasons for the hickup.

And with wifi , causes might just be radio-waves from all sorts of sources.
But OpenWRT and the GL.inet implementation all have their own causes, release/version/device dependent.

13

Hello.

Regretfully I have no instruments suitable for checking the spectrum quality around the devices.
My smaller spectrum analyzer just reaches up to 2.1GHz.
The other reaches 16GHz, but is pretty old and is too much heavy and bulky for me to take home.

Anyway, after the weekend i'll be back home and I hope the issue presents itself so I can capture logs.

thank you.
E.

14

Well done, but my SFT1200 does not react on wifi power setting, if uplink is used.

Quite some free APPs on a smartphone (eg Wifi Analyzer) do good spectrum scans. Also on a PC this is possible. (I use inSSIDer from MetaGeek, and NetSpot and Wi-Fi Scanner on a Windows11 PC)

15

hi, Bruce. How can I email the logs to you?
By the way, in the meanwhile i found some "repeatability" of issues when i start my firestick.
Looking at the available networks it seems some "vanish" when i start the firestick and come back after a while i removed it.
anyway, i logged teraterm output (sorry, it was faster than scp) and i can send it to you. let me know how.

in the logs i see some errors , even if i can't tell if its righteous errors or just debug informations.

thank you

16

Please create a PM and send to @weiming.he and me, thank you!

Is the firestick a TV HDMI streaming device?
Why does "available networks" disappear when it starts?

17

i tried to send email , i dont know if i did iti correctly (could not find a pm button).

Firestick is an hdmi device. (it's Amazon's device).
I have several of them (connecting to different mango and to the beryl to use vpns).

What i noticed is that sometimes, starting firesticks causes some wifi to vanish.
I use "wifiman" on the mobile to see wifi names and part of them are gone, part remains.

This effect is not immediate (like, plug - vanish).
After a while (after booting, showing some video such as program advertise and in general behaving normally) the firestick says "no connection".
At that point wifis vanished (not only mine, also some other i normally see around..).
Waiting the connection goes up and down. sometime resumes and sometimes not.

Note that this is not "always happening"... it's however the only "repeatable" event that sometimes trigger all my problems with the contraption i described at the begin of this post.

thank you for any insight.
have a good day
E.

18

We got the PM, and R&D is checking.

When Firestick is starting/started, in addition to GL router, will the SSIDs of other routers/APs disappear?

a bit strange, how can Firestick affect the Wi-Fi wireless radio...

19

Good morning, Bruce.
Thank you for letting me know you got my email. I'll be waiting for your colleagues feedback.

Concerning 'how can a firestick disrupt wifi', it also sounds very strange,being a certified device from a very reputable company. Should this happen often, many customers would be upset and forums would let this very clear.
As I said, however this was the only trigger to some of the disruptions.

Where I live there are several wifis around, many very faint, those fainter ones tends to disappear too, but I can't tell if it's because they are just too faint or because some device is wreaking havoc in the frequency band.

I work in electronics but I have no instruments to check the spectrum in that range of frequencies.

I'll be waiting your feedbacks, thank you.

E.

1 Like
20

FireStick is a wifi device. Even if not functioning as AP but as station, it emites wifi signals.

We are used to fight weak wifi signal problems, much less concerned about too strong wifi signals.

But too strong can be a major problem (I had visiting GL.inet travel router killing my infrastructure AP's because they where too close.) My Mikrotik AP does measure the received signal and when above -30dB (eg -28dB) the receiver of the AP was saturated, even if the other device was on a different channel in that 2.4 or 5 GHz band. (Saturation of receiver happens before the channel separation, once saturation happens all received signal is distorted and invalid . Wifi is two-way communication so that saturated receiver will block sent and received information)

Set two wifi devices only 30 cm apart , emitting at the allowed +20dBm and they will saturate each other! Wifi stops functioning ! AP beacons are totally distorted and not recognised anymore. AP SSID disappears from the list. (They only disappear after a timeout, because the client caches that information for a while)

If you have a smartphone or PC you have all the instruments needed to measure. Use some APP on the smartphone that shows wifi around (Wifi Analyzer on Android, InSSIDer, WI-FI scanner, or NetSpot on PC). Interpretation is not that simple because you need to know what the FireStick and your Mango is receiving, not your measuring device. (Mango should however show signal strength in LUCI or SSH interface). Anything stronger than -30dBm is a major problem. Mango (OpenWRT) will only report on the strength of the channel connected to, another channel could be the cause of the problem.

Signal strength changes with the distance, double distance is 6dBm less (4x weaker signal), half the distance is 6dBm more (4x stronger). Good signal is between -40dBm (maximum) and -80dBm (minimum).

A flatscreen TV can reflect the wifi signal, doubling the received signal (+3dBm) if near the devices.

If the FireStick is a +20dBm device, what I expect, then 1 meter apart will be needed, as minimum.

I see the same issue happening with Chromecast devices, and the router behind the TV set.

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22

To anyone who might be concerned, the final solution has been to move the problematic streaming device to an AP with a 5 GHz band (in this case, an Opal).

Starting the remote device in a particular position led to an increase in channel errors and, ultimately, the failure of the connection.
Many inspections have been tried, many logs checked, and some surprising findings found (such as an increase in temperature for wifi devices as soon as the troubles start to happen)

As bpwl1 hinted, it is likely that something in my home might act as a reflector or, in any case, cause pollution of the spectrum/channels and a fight for transmission among devices.

Tired of the headaches, I replaced one Mango with an Opal (GL-SFT1200), disabling its 2.4G band and connecting the firesticks on the 5Ghz band only.

It's not elegant (hunting down and solve the cause would be better) but it's effective with a marginal cost and saved headaches.

It's all
Eli.

1 Like