Disconnect on modem-no-carrier repeated every 60 seconds

Duane Murphy duane.murphy at mainspringenergy.com
Tue Aug 31 16:46:49 UTC 2021

We are seeing an installation where we the connection is disconnected every 60 seconds due to 

state change: activated -> failed (reason 'modem-no-carrier', sys-iface-state: 'managed')

I have included an excerpt of one of the 60 second transitions from failed back to failed. 

What would cause the connection to disconnect and immediately reconnect, then take 60 seconds to disconnect again?

I could believe that this site does not have great reception, however, I'd like to understand the continuous cycle and what we may be able to do about the cycle; either remain connected or don't connect at all. This cycling is hard on the network systems.  (Note the site is a fixed location for cellular modem.)

Here's the particulars about the system:

Ubuntu 18.04
NetPlan with NetworkManager as the renderer 
This allows us to integrate the modem connection with the usual ethernet connections
mmcli 1.10.0

From mmcli --modem -

  Hardware |   manufacturer: Sierra Wireless, Incorporated
           |          model: Sierra Wireless EM7455 Qualcomm� Snapdragon? X7 LTE-A
           |       revision: SWI9X30C_02.24.05.06
           |   h/w revision: EM7455
           |      supported: gsm-umts, lte
           |        current: gsm-umts, lte

Thank you for any help you might be able to offer so that I can understand what is happening. 


Duane Murphy | Software Engineer | Mainspring Energy <http://mainspringenergy.com/>

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