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koroknai
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Joined: Wed Apr 27, 2022 2:52 pm

lte interface stops working after switching to other sim slot

Wed Apr 27, 2022 3:57 pm

Product: Mikrotik LtAP mini LTE kit GSM Router
- modifications: we use external lte antenna.
Our goal: we would like to use the kit as a dual sim router. We made a sim switcher script. We use telnet to log in, and run the sim switch function.
This configuration exists on 38 places in the city, and works well most of the time.
But after a few weeks we had to replace 6 routers because one reason: after rebooting the device, the lte interface is not showing up.
- we tried os update, did not solve the problem
- sometimes (1% of the time) the interface comes alive, but after switching to the other sim or rebooting the device (when the lte interface has to reboot), the lte interface do not comes alives no matter what
- at two of these devices we experienced that, if we insert just one sim card, the interface works. However we have to use 2 sim cards, so we tried again and the interface stopped working with 2 sims.
We used the latest fw at the time (routeros-mipsbe-6.49.2).
I am concerned about the future use of the devices. With one sim card we had no problem in years.

Does anyone had same experience? Or is there anybody who can give some advice?
I can provide more detailed information if needed.
Thank you!
 
sunnysky
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Re: lte interface stops working after switching to other sim slot

Mon May 09, 2022 12:08 pm

Hi koroknai,

I'm observing very similar situation with one of mine LtAP mini LTE kit router (one out of ten so far)
Symptoms are the same generally - after reboot or switching modem slot, LTE interface just get lost.
I turned on additional lte-logging and you can see the result on the screenshot.

At 01:14:08 LTE interface was present and ROS had been actively complaining about SIM absence (that was true, but it does not really matter)
Then I tried to switch sim slot (at 01:14:09), LTE interface disappeared (it's ok) and ... nothing then... and it's NOT OK
As you can see, I had been waiting quite a long time, but almost two hours later... still nothing.
Then I switched sim-slot back - and nothing had happen again
In this state (when lte is absent) usb2 port marked as invalid.
USB power reset does not help.
LtAP mini modem issue 1.png
P.S. I observed the same issue with sim-cards were installed in both slots as well that's why I think it does not relate to possible sim-card issue.
I tried this slot switching exercise with another LtAP mini that I currently have on board and it goes without any issues.

Here was a suggestion regarding possible power issue when running on microUSB, but I played with powering from microUSB and from standard power supply - all the same.
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koroknai
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Re: lte interface stops working after switching to other sim slot

Mon Jun 13, 2022 12:05 pm

Hi Sunnysky!
I tried using both of the power sources, unfortunately I had no luck with it still not working properly.
Is there any bug report function on Mikrotik site?
 
koroknai
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Re: lte interface stops working after switching to other sim slot

Thu Sep 08, 2022 12:50 pm

I just discovered a workaround.
I developed a scheduled script. It checks in every 30 seconds the lte interface is available or not. If not, it changes the sim-slot twice. Setting up and after down the sim slot, or vica versa (down after up), do the trick for me.
Example:
- sim slot already set to up
- if no lte1 interface is present, the script set the slot to down, then sets again to up.
- sometimes it gets up after 1 resetting cycle, somtimes it needs 2 or 3 resets.
I tested this solution on OS V7.4.1. Because after I installed the V7 OS, the LTE board updated ot a newer firmware.
In the future it would be great to have a fix from Mikrotik, however until it is not fixed this solution is works for me.

The same script is not working for V6 and V7 OS, because they moved the settings. Here are some examples:
V6: /system routerboard modem set sim-slot=down
V7: /interface lte settings set sim-slot=down

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