ModemManager 1.16.2 connection issue for EM7455 Sierra Modem

Alejandro Vega alexvega48 at
Mon Jul 5 11:30:57 UTC 2021


After making more tests and checking the logs more carefully I have found
differences between the connection sequence , specifically regarding the
bearer options.
When a bearer is created with no auth options, like following the next
command  ( 'allowed-auth' methods are not set):

*mmcli -m 0 --create-bearer="apn=myapn,user=myuser,password=

If we try to connect afterwards using the recently created bearer:

*mmcli -m 0 -b 0 -c*

Behaviour in ModemManager 1.10:

*ModemManager[5096]: <debug> [1625232197.783697] Using default (PAP)
authentication methodModemManager[5096]: <debug> [1625232197.783715]
Launching ipv4v6 connection with APN*

Behaviour in ModemManager 1.16.2:

*ModemManager[15247]: <debug> [1625483530.597060] [modem0/bearer0] using
default (CHAP) authentication methodModemManager[15247]: <debug>
[1625483530.597085] [modem0/bearer0] launching ipv4 connection with APN
' <>'*

And this is causing my modem to fail when attempting a connection. *If I
create the bearer in ModemManager 1.16.2 specifying "allowed-auth=pap", it
works. *
Therefore, before it was not needed to specify the authentication method if
it was PAP, now it seems to be a need.

Note that in both versions the "Provisioned contexts" LOG (where the bearer
info appears) is the same, however, when launching the connection there are

Hope this helps.


El dom, 4 jul 2021 a las 23:16, Aleksander Morgado (<
aleksander at>) escribió:

> Hey,
> >
> > 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.
> --
> Aleksander

Un saludo.

Alejandro Vega
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