LE910 connection with custom APN on AT&T SIM

[Bjørn Mork]

Nate Pleasant <nate.pleasant at accelerated.com> writes:

> I have a Telit LE910 modem that ModemManager doesn't seem to be able
> to connect with when using an AT&T SIM card with a custom APN.  See
> output and debug messages below for reference.  If I connect this same
> SIM card with a Sierra MC7354 or Sierra MC7455 modem, it's able to
> connect with ModemManager just fine.  Is there something I'm missing
> when connecting with this Telit LE910 modem?

I hope some Telit experts will chime in if I am wrong but the LE910 is
based on an Intel chipset, isn't it?

If so, then I think some of the findings wrt the Sierra Wireless EM7345
are relevant. My memory is foggy at best, but I found this:
https://lists.freedesktop.org/archives/libmbim-devel/2014-May/000283.html

There were a few surprises (to me at least) there.  I don't know how
much of that has been fixed/changed in newer firmware revisions.  But
some issues to be aware of:

- the modem might bring up a default bearer using some APN you never
 configured, based on the SIM/operator.

- this default bearer can conflict with later attempts to connect other
  APNs using MBIM and the same IP-type.  Note that in my case I could
  easily detect this error since I knew the two APNs used different
  address types (global vs rfc1918)

- you might be able to work around the issues by explictly configuring
  contexts before attempting to do an MBIM connect.


My proposal is to play with the AT+CGDCONT list and see if it changes
the behaviour in any way.



Bjørn