linux-f9t1:/var/log # journalctl -f
-- Logs begin at Mi 2016-03-09 16:51:15 CET. --
Mär 10 17:43:27 linux-f9t1 ModemManager[1178]: <info>  Modem /org/freedesktop/ModemManager1/Modem/6: state changed (enabling -> registered)
Mär 10 17:43:27 linux-f9t1 NetworkManager[1581]: <info>  (ttyUSB2): modem state changed, 'enabling' --> 'registered' (reason: user-requested)
Mär 10 17:43:28 linux-f9t1 NetworkManager[1581]: <info>  (ttyUSB2): Activation: starting connection 'AldiTalk/MedionMobile' (50927a88-446f-459c-82ed-e9e0658a1e94)
Mär 10 17:43:28 linux-f9t1 NetworkManager[1581]: <info>  (ttyUSB2): device state change: disconnected -> prepare (reason 'none') [30 40 0]
Mär 10 17:43:28 linux-f9t1 NetworkManager[1581]: <info>  NetworkManager state is now CONNECTING
Mär 10 17:43:28 linux-f9t1 NetworkManager[1581]: <warn>  (ttyUSB2): Failed to connect 'AldiTalk/MedionMobile': Connection requested both IPv4 and IPv6 but dual-stack addressing is unsupported by the modem.
Mär 10 17:43:28 linux-f9t1 NetworkManager[1581]: <info>  (ttyUSB2): device state change: prepare -> failed (reason 'modem-init-failed') [40 120 28]
Mär 10 17:43:28 linux-f9t1 NetworkManager[1581]: <info>  NetworkManager state is now DISCONNECTED
Mär 10 17:43:28 linux-f9t1 NetworkManager[1581]: <warn>  (ttyUSB2): Activation: failed for connection 'AldiTalk/MedionMobile'
Mär 10 17:43:28 linux-f9t1 NetworkManager[1581]: <info>  (ttyUSB2): device state change: failed -> disconnected (reason 'none') [120 30 0]