Static vs DHCP setups from ModemManager in OpenWrt

Peter Naulls peter at
Thu Jul 15 20:13:48 UTC 2021

On 7/15/21 3:54 PM, Aleksander Morgado wrote:
>>>> After restart of ModemManager and then ifup wwan, reconnection is successful.

> Oh, is this AT+PPP based really? You should have started from there :)
> Being a Quectel chipset, is it by any chance Qualcomm based and you
> could use QMI instead of AT+PPP? Or is QMI not available? What about
> MBIM? Anything better than AT+PPP will definitely give you less
> headaches.

Ah yes, I wasn't paying attention.  It is QMI, but I have seen it
try to use ppp in certain error states like this.

> Sometimes, though, this is the only way to recover. Sometimes you may
> be able to recover just by forcing an IMSI detach and re-registration
> (e.g. going into low-power mode temporarily); some other times you can
> recover requesting a module reset in a controlled way via AT or QMI,
> some other times you may need to instead toggle the RESET pin, and the
> last and most drastic solution is always to fully cut power.

Yes, and also cycle the USB hub as I mentioned.  My previous testing
on this shows that this is the only fully reliable solution, perhaps
due to additional USB controller bugs.

> The openwrt integration does not have per se a way to attempt to
> recover "dead" modems, or modems that by one reason or another don't
> connect any more. I've worked preparing multiple types of setups like
> those and I've always written customized "wwan monitor" programs to do
> that, depending on how the modem is integrated in the system.

Right. Well, I'd still be interested in what can be done here in
some of the cases I mentioned.

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