Cinterion PLS8-X, udhcp fails

[José]

I am trying to use a Cinterion PLS8-X with ModemManager. The modem is
properly identified and enabled, and the connection is properly
established. But when I try to use the network interfaces and get an
IP from the DHCP server, it fails to get any IP address.

This is the log:

root at ccimx6sbc:~# ModemManager &
root at ccimx6sbc:~# ModemManager[827]: <info>  ModemManager (version
1.4.12) starting in system bus...
ModemManager[827]: <info>  Creating modem with plugin 'Cinterion' and '7' ports
ModemManager[827]: <warn>  Could not grab port (tty/ttyACM4): 'Cannot
add port 'tty/ttyACM4', unhandled serial type'
ModemManager[827]: <warn>  Could not grab port (tty/ttyACM3): 'Cannot
add port 'tty/ttyACM3', unhandled serial type'
ModemManager[827]: <warn>  Could not grab port (tty/ttyACM2): 'Cannot
add port 'tty/ttyACM2', unhandled serial type'
ModemManager[827]: <info>  Modem for device at
'/sys/devices/soc0/soc.0/2100000.aips-bus/2184200.usb/ci_hdrc.1/usb1/1-1/1-1.1'
successfully created
ModemManager[827]: <info>  Modem: state changed (unknown -> disabled)

root at ccimx6sbc:~#
root at ccimx6sbc:~#
root at ccimx6sbc:~# mmcli -m 0 --simple-connect=movistar.es
Error parsing connect string: 'Couldn't find equal sign separator'
root at ccimx6sbc:~# mmcli -m 0 --simple-connect=apn=movistar.es
ModemManager[827]: <info>  Simple connect started...
ModemManager[827]: <info>  Simple connect state (3/8): Enable
ModemManager[827]: <info>  Modem
/org/freedesktop/ModemManager1/Modem/0: state changed (disabled ->
enabling)
ModemManager[827]: <info>  Modem
/org/freedesktop/ModemManager1/Modem/0: 3GPP Registration state
changed (unknown -> registering)
ModemManager[827]: <info>  Modem
/org/freedesktop/ModemManager1/Modem/0: 3GPP Registration state
changed (registering -> home)
ModemManager[827]: <info>  Modem
/org/freedesktop/ModemManager1/Modem/0: state changed (enabling ->
registered)
ModemManager[827]: <info>  Simple connect state (4/8): Wait to get fully enabled
ModemManager[827]: <info>  Simple connect state (5/8): Register
ModemManager[827]: <info>  Simple connect state (6/8): Bearer
ModemManager[827]: <info>  Simple connect state (7/8): Connect
ModemManager[827]: <info>  Modem
/org/freedesktop/ModemManager1/Modem/0: state changed (registered ->
connecting)
ModemManager[827]: <info>  Modem
/org/freedesktop/ModemManager1/Modem/0: state changed (connecting ->
connected)
ModemManager[827]: <info>  Simple connect state (8/8): All done
successfully connected the modem
root at ccimx6sbc:~# mmcli -m 0

/org/freedesktop/ModemManager1/Modem/0 (device id
'f19bc7567e36f9fef0e5998b5f6a9f7346785ec1')
  -------------------------
  Hardware |   manufacturer: 'Cinterion'
           |          model: 'PLS8-X'
           |       revision: 'REVISION 03.003'
           |      supported: 'gsm-umts, lte'
           |        current: 'gsm-umts, lte'
           |   equipment id: '004401081420651'
  -------------------------
  System   |         device:
'/sys/devices/soc0/soc.0/2100000.aips-bus/2184200.usb/ci_hdrc.1/usb1/1-1/1-1.1'
           |        drivers: 'cdc_acm, cdc_ether'
           |         plugin: 'Cinterion'
           |   primary port: 'ttyACM1'
           |          ports: 'ttyACM1 (at), ttyACM0 (at), usb0 (net),
usb1 (net)'
  -------------------------
  Numbers  |           own : 'unknown'
  -------------------------
  Status   |           lock: 'none'
           | unlock retries: 'sim-pin (3), sim-pin2 (3), sim-puk (10),
sim-puk2 (10), ph-net-pin (10), ph-net-puk (32), ph-fsim-pin (10),
ph-fsim-puk (32)'
           |          state: 'connected'
           |    power state: 'on'
           |    access tech: 'edge'
           | signal quality: '20' (recent)
  -------------------------
  Modes    |      supported: 'allowed: 2g; preferred: none
           |                  allowed: 3g; preferred: none
           |                  allowed: 2g, 3g; preferred: none
           |                  allowed: 2g, 3g, 4g; preferred: none'
           |        current: 'allowed: any; preferred: none'
  -------------------------
  Bands    |      supported: 'egsm, dcs, pcs, g850, u1900, u850'
           |        current: 'egsm, dcs, pcs, g850, u1900, u850'
  -------------------------
  IP       |      supported: 'ipv4, ipv6, ipv4v6'
  -------------------------
  3GPP     |           imei: '004401081420651'
           |  enabled locks: 'none'
           |    operator id: '21407'
           |  operator name: 'Movistar'
           |   subscription: 'unknown'
           |   registration: 'home'
  -------------------------
  SIM      |           path: '/org/freedesktop/ModemManager1/SIM/0'

  -------------------------
  Bearers  |          paths: '/org/freedesktop/ModemManager1/Bearer/0'

root at ccimx6sbc:~# mmcli -
root at ccimx6sbc:~# udhcpc -i usb0
udhcpc (v1.23.2) started
cdc_ether 1-1.1:1.10 usb0: CDC: unexpected notification 01!
Sending discover...
Sending discover...
^C
root at ccimx6sbc:~# udhcpc -i usb1
udhcpc (v1.23.2) started
cdc_ether 1-1.1:1.12 usb1: CDC: unexpected notification 01!
Sending discover...

Any idea why the CDC ether driver warns about that unexpected
notifications, and why is the dhcp client not working?