new problems with connecting with an LTE modem

[Bhima <bhima pandava gmail com>]

Hi Guys!

I'm having problems with a Sierra MC7710 LTE modem, running in a Soekris 
Net6501, after a recent update to Ubuntu 16.04 to the 4.4.0-22-generic 
kernel.  For the past few years I've been using the qmi-network helper 
script to connect cdc-wdm0, which in turn created a wwan0 port.  Now 
that's all gone pear shaped and I've gone around in circles trying 
figure out what's gone wrong.

looking in dmesg, I see that wwan0 is actually getting renamed to 
wwp2s2f3u3i8, which is confirmed by status returned by "mmcli -m 0" 
(ports: 'ttyUSB0 (qcdm), ttyUSB2 (at), cdc-wdm0 (qmi), wwp2s2f3u3i8 
(net)').  I can get a dhcp address on 'wwp2s2f3u3i8' but the throughput 
on the resulting channel is severely constrained.

So now I'm wondering what exactly the proper way to configure and use 
this modem from the command line these days.


Thanks!