Cellular Connection breaks down when I set up a wlan bridge

After I set up a wlan hotspot and bridge on my Rasperry as explained in the tutorials Setting up a Raspberry Pi as an LTE Hotspot

the connection to the internet breaks up after a few seconds or minutes. I still can connect to the wlan hotspot I created, however with no Internet access. It takes a reboot to re-establish the cellular internet connection, until it breaks again after a few seconds.
Interestingly, on the connect.sixfab portal, the only interface listed is the bridge br0, wwan0 and wlan0 interfaces disappear as soon as I have the hotspot enabled.
In mincom, AT#ECM=1,0 returns an error.
When I disable the hotspot, and return to factory settings, the cellular connection works flawlessly.

In the meantime I reconfigured the bridge to use the eth0 lan cable connection to the internet instead of the wwan0 interface. The access point and bridge to eth0 are operating flawlessly. And all of a sudden, the wwan0 interface appears again in the sixfab connect portal as connected.
So the issue is likely with the sixfab code somewhere which doesn’t allow the creation of a bridge between a wlan access point and the wwan0 interface.

I am on a clean Debian Bullseye image, Rasperry 3+
Any ideas how to debug?


CORE does not support the hotspot tutorial you mentioned. That’s why I recommend you uninstall CORE and follow it on a clean image.

ok thanks. What do you mean by “follow it on a clean image”?
I currently have a fresh Raspy Bullseye image, Core is not yet installed.
What shall I do next?

Ok then no problem, you can follow the tutorial.

OK thanks a lot. I followed the instructions with sixfab core not installed, and now I have my access point and bridge over to wwan0 up and running. That looks good!
Next question:
Obviously, since the Core is no longer installed, I cannot see the device anymore in sixfab.connect portal. Also, I do not see any usage statistics.
With the bridge configured, is there any chance to remotely monitor the device status?

@ensar I got the bridge working as I need it for my project - so far so good.
I have 2 remaining issues:

  1. After reboot, the modem is not connected to the cellular network. I need to establish the connection by sending AT#ECM=1,0 manually in minicom after each reboot/disconnect.
    I would like to automate this, eg by a cron job. However the atcom utility I wanted to use does not work for me - see also the GH issue I created atcom cannot connect to Telit modem · Issue #19 · sixfab/atcom · GitHub

  2. I do not see any usage data in the SixfabConnect portal. My SIM is listed, but I do nor see any statistics - its all zero for the entire time since I have activated the card.

EDIT: I could resolve issue#1 (see my issue statement on your github).

So the remaining problem for me is the missing usage and billing information.

Could you PM me your SIM ICCID and the e-mail you are logged into?