ModemManager 1.16.2 connection issue for EM7455 Sierra Modem

Aleksander Morgado aleksander at
Sun Jul 4 21:16:16 UTC 2021


> I have installed ModemManager version 1.16.2 recently in order to use the latest functionalities and I have been experiencing an issue after trying to connect to a custom APN (within a VPN).
> The issue is that the modem is unable to transition from the registered to the connected status and finishes the connection attempt immediately just after querying a connection command. Using commercial sims with other APNs (which normally don't have user and password, don't know if that matters) it does not  happen. I am using a EM7455 Sierra Wireless Modem.
> Until now , I have been working with ModemManager 1.10.6 under MBIM mode and have been able to connect with no problems with different types of sims (commercial and custom APNs).
> Attached tests (MM in Debug mode)
> 3 x tests with the MM 1.16.2 working under QMI mode (x1) and MBIM mode (x2 with different errors) but being unable to connect.
> 1 x test with MM 1.10.6 working under MBIM mode and same bearer configuration  , modem is able to connect
> In order to create the bearer and make tests I am always using this custom APN I mention:
> mmcli -m 0 --create-bearer=",user=*******,password=******,ip-type=ipv4"
> mmcli -m 0 -b 0 -c
> Is there anything I should consider changing regarding the connection attempt ? Shall I perform any additional configuration prior to the connection in MM 1.16.2 ?

I don't think you would need anything special, truth be told. If the
modem was connecting fine with 1.10, it should connect equally fine
with 1.16.

> I found a thread where similar errors appear
> but I believe it is already merge into MM 1.16.2

That branch adds support for configuring the initial EPS bearer
settings in QMI modems, I don't think that would affect in any way
your issue here.

I'm afraid I don't have time to dig into 4 different connection logs
to try to find differences between them; could you please do that
yourself and try to compare the working MM 1.10 MBIM connection
sequence with the failing MM 1.16 MBIM connection sequence and try to
find what the differences are? If there are no differences, the
connection should equally succeed.


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