Device constantly re-authenticating and switching between 2.4 GHz/5GHz
We encountered issues when playing music via Airplay.
The Access point log shows devices (all iOS) which authenticate themselves on the AP every 1-5 minutes. When doing this, they constantly keep switching between 2.4 GHz and 5 GHz.
06.10.22 20:47:28 [fritz.powerline] WLAN-Gerät hat sich neu angemeldet (2,4 GHz), 144 Mbit/s, PC-192-168-178-170, IP 192.168.178.170, MAC 26:16:86:06:8A:0C.
06.10.22 20:47:10 [fritz.powerline] WLAN-Gerät hat sich neu angemeldet (5 GHz), 866 Mbit/s, PC-192-168-178-170, IP 192.168.178.170, MAC 26:16:86:06:8A:0C.
06.10.22 20:44:44 [fritz.powerline] WLAN-Gerät hat sich neu angemeldet (2,4 GHz), 144 Mbit/s, PC-192-168-178-170, IP 192.168.178.170, MAC 26:16:86:06:8A:0C.
06.10.22 20:44:34 [fritz.powerline] WLAN-Gerät hat sich neu angemeldet (5 GHz), 866 Mbit/s, PC-192-168-178-170, IP 192.168.178.170, MAC 26:16:86:06:8A:0C.
("WLAN-Gerät hat sich neu angemeldet" means "Wifi device has re-authenticated")
I recorded the following traces:
- WIFI Management frames: https://drive.google.com/file/d/10OFZ...
- 2.4 GHz interface: https://drive.google.com/file/d/1-Zg3...
- 5 GHz interface: https://drive.google.com/file/d/1jhU3...
I would be happy to find out the following:
- What keeps triggering the device to constantly re-authenticate and keep switching frequency?
- Why does this switching behavior only occur when playing music via Airplay?
Background info:
- All devices and AP in the same room, max distance to AP 3 meters.
- The AP (Fritz Powerline 1260) is part of a so called "Mesh and is connected to the "Mesh Master" (Fritz!Box 7590) via Powerline.
- Almost no other wifi networks nearby.
UPDATE
Each time before the device re-authenticates, it receives a Disassociation frame from the AP with either one of the following reason codes:
- Previous authentication no longer valid (0x0002): This is not being sent to other devices. How to interpret this?
- Disassociated because sending STA is leaving (or has left) BSS (0x0008): The device remained in the same room all the time. Does this indicate a poor radio signal?
Can you get a real OTA (over the air capture) from a third party device? Preferably on both channels (on the two bands) but even one at a time would be a good a start.
One hypothesis is beacon loss, but no beacons are present to confirm or reject. Client associates with a specific BSSID then issues an Authentication frame to the alternate BSSID (other channel). This forces the AP to disassociate the client and then it starts all over when the original BSSID figures out the client left, and disassociates the client again.
Something to try: disable one of the bands for this SSID and is it then stable?
Thanks, I'll try to record an OTA.
You write: ... when the original BSSID figures out the client left, and disassociates the client again.
I guess that's the point where it sends disassociation frame Previous authentication no longer valid (0x0002)? What makes me wonder is the AP should know that the client is already associated on the other channel (as it all happens on the same AP), therefore I would suppose there's no need to disassociate the client.
As suggested by @Bob Jones, I recorded an OTA on 2.4 GHz (channel 6).
Again it shows one device constantly switching between 2.4 GHz and 5 GHz.
AP log (log entry 13.10.22 20:32:27 marks the first time when the device switches, this goes on for about one hour):
(more)@Bob Jones: please see https://ask.wireshark.org/question/28...
The OTA capture is missing a lot of QoS-Data frames but I don't think having those is going to shed much more light on the problem. I see the capture is taken at the AP and the channel utilization and signal strength look OK for the client.
I couldn't find any obvious triggers to the problem but it does appear to be a client issue. You can't rule out something that the AP is doing to trigger the behavior but until that is found, I would focus on client behavior. Can you get a log for the client? Maybe it will tell you why it is choosing to do what it is doing?