PDP settings for LTE only network

[Brendan Simon]

Hi Aleksander,

Many thanks for your response.  That is a BIG BIG HELP -- as I currently 
have to stop the MM service and restart it in debug mode, just to query 
some settings.  I then change settings if necessary and then 
stop/restart MM in non-debug mode.  All that takes a bit of time.

I've just discovered that MM 1.18.0 is available in `buster-sloppy` 
distro - part of Debian Backports, so that looks like the way forward 
for now.

Again, many many thanks !!

Cheers, Brendan.
--


On 14/6/2022 6:01 pm, Aleksander Morgado wrote:
> Hey,
>
> On Tue, Jun 14, 2022 at 9:53 AM Brendan Simon<Brendan at brendansimon.com>  wrote:
>> Hello,
>>
>> I have a number of embedded linux boxes with Quectel EC21 4G modems, connected to various cellular networks (AT&T, Verizon, ...).
>>
>> AT&T are removing 3G from some areas and the modems are not reconnecting.  My devices are vanishing off the face of the Internet.
>>
>> Quectel have provided some assistance and guidance and advised to configure some settings for AT&T Sunsetting.  The UE Usage Setting was changed to configure the device as Data Centric (i.e. no voice), however it did not resolve the issue.
>>
>> AT&T provided some assistance - apparently the APN was wrong.  Seems like some generic APNs are being used and not the APN specified in the NetworkManager configuration.  This all worked ok when 3G was available.
>>
>> AT&G also suggested the PDP settings of the modem are the issue.
>> Changing the default PDP context (#!) from an APN of "" to the provided APN seems to have resolved the connection issue.
>>
>> I have used `mmcli -m N --command="..." to modify the PDP context for testing.
>>
>> I feel this is hacky and shouldn't be required.
>>
>> Is there a better (more elegant and generic method) to set the PDP contexts so modems (preferably any brand) will work on 4G only networks?
>>
> The way to elegantly change the APN settings for the initial EPS
> default bearer would be using e.g.:
> $ mmcli --3gpp-set-initial-eps-bearer-settings='apn=something'
>
> In QMI-based modems as the EC21, this would internally change the
> profile associated to the initial bearer.
>
>> NOTE: we are using Debian Buster with ModemManager 1.10.0.
>>
>> Would upgrading MM help?  Buster-Backports has 1.14.0 available, which would be easy to build/install on the existing OS.
>>
> The QMI-based initial EPS bearer settings update was implemented in
> commit 5613215db8 (November 2020), which was released with
> ModemManager 1.16.0. The latest update in the 1.16.x series is
> 1.16.10, but the series is now fully unsupported; the latest supported
> series is 1.18.x.
>
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