mobile broadband requires NetworkManager restart to work

[smores]

Hello,

I'm summarizing the most important information (according to my judgement) first before going into detail.

Problem:
My USB mobile broadmand dongle can not connect to the network unless NetworkManager is restarted (i.e. NetworkManager start with the dongle already plugged in). I'd like to use the USB dongle w/o restarting NetworkManager.

Steps to reproduce:

1. make sure USB mobile broadband dongle is unplugged
   
2. make sure NetworkManager is started
   
3. plug in USB mobile broadband dongle (and wait until it is noticed by NetworkManager)
   
4. try to connect to preconfigured mobile broadband network with NetworkManager (via nm-applet) => connection fails
   
5. restart NetworkManager (/etc/init.d/NetworkManager restart; the USB dongle stays plugged in)
   
6. try to connect to preconfigured mobile broadband network with NetworkManager (via nm-applet) => success (can browse web, etc.)
   

most visible error messages:

• ModemManager[2800]: <warn> (ttyUSB0): port attributes not fully set
  
• (1) Creating object for path '/org/freedesktop/NetworkManager/ActiveConnection/1' failed in libnm-glib.
  
• Failed to connect 'O2 Pay-by-MB': Connection requested IPv4 but IPv4 is unsuported by the modem.
  

Additional Details:

• I use fluxbox, so I may miss an important service/daemon that is responsible for correct information passing between NetworkManager and other services despite my best efforts.
  
• When fluxbox starts, it runs dbus-launch nm-applet &
  
• The USB mobile broadband modem in question is a Huawei E173
  
• The preconfigured mobile broadband connection is called O2 Pay-by-MB and successfully connects if NetworkManager is started with the USB dongle plugged in
  
• When failing to connect to the mobile broadband network, iIn addition to the log messages a window pops up that reads (1) Creating object for path '/org/freedesktop/NetworkManager/ActiveConnection/1' failed in libnm-glib.
  
• I also have, among other processes, the following processes running (while being connected via mobile broadband)
  

  Code:

  ps -A   PID TTY          TIME CMD   ...   606 ?        00:00:00 cfg80211  1246 ?        00:00:00 ipv6_addrconf  1554 ?        00:00:00 systemd-udevd  1603 ?        00:00:01 irq/46-iwlwifi  2767 ?        00:00:00 dbus-daemon  2795 ?        00:00:00 wpa_supplicant  2797 ?        00:00:00 polkitd  2800 ?        00:00:06 ModemManager  2831 ?        00:00:13 acpid  2853 ?        00:00:00 console-kit-dae  3774 ?        00:00:00 slim  4064 ?        00:00:04 fluxbox  4088 ?        00:00:00 dbus-launch  4089 ?        00:00:00 dbus-daemon  4108 ?        00:00:02 nm-applet  4115 ?        00:00:00 dbus-daemon  4152 ?        00:00:00 dbus-daemon  5164 ?        00:00:00 gnome-keyring-d  6585 ?        00:00:01 NetworkManager  6623 ?        00:00:00 pppd  7405 ?        00:00:00 notification-da   ...

  
  

Log messages:
Following the above mentioned steps to reproduce my problem, the following logs will appear (incrementally) in /var/log/message:

1. make sure USB mobile broadband dongle is unplugged
   
2. make sure NetworkManager is started
   
3. plug in USB mobile broadband dongle (and wait until it is noticed by NetworkManager)
   

   Code:

   Aug  2 08:10:59 cow kernel: usb 1-2: new high-speed USB device number 8 using xhci_hcd Aug  2 08:10:59 cow kernel: usb 1-2: New USB device found, idVendor=12d1, idProduct=1446 Aug  2 08:10:59 cow kernel: usb 1-2: New USB device strings: Mfr=3, Product=2, SerialNumber=0 Aug  2 08:10:59 cow kernel: usb 1-2: Product: HUAWEI Mobile Aug  2 08:10:59 cow kernel: usb 1-2: Manufacturer: HUAWEI Technology Aug  2 08:10:59 cow kernel: usb-storage 1-2:1.0: USB Mass Storage device detected Aug  2 08:10:59 cow kernel: scsi host13: usb-storage 1-2:1.0 Aug  2 08:10:59 cow kernel: usb-storage 1-2:1.1: USB Mass Storage device detected Aug  2 08:10:59 cow kernel: scsi host14: usb-storage 1-2:1.1 Aug  2 08:10:58 cow laptop-mode[5956]: Laptop mode Aug  2 08:10:58 cow laptop-mode[5957]: enabled, not active Aug  2 08:10:58 cow laptop-mode[5989]: Laptop mode Aug  2 08:10:58 cow laptop-mode[5990]: enabled, not active Aug  2 08:10:58 cow usb_modeswitch[6010]: switch device 12d1:1446 on 001/008 Aug  2 08:11:00 cow kernel: usb 1-2: USB disconnect, device number 8 Aug  2 08:10:58 cow laptop-mode[6107]: Laptop mode Aug  2 08:10:58 cow laptop-mode[6108]: enabled, not active Aug  2 08:10:58 cow laptop-mode[6140]: Laptop mode Aug  2 08:10:58 cow laptop-mode[6141]: enabled, not active Aug  2 08:11:04 cow kernel: usb 1-2: new high-speed USB device number 9 using xhci_hcd Aug  2 08:11:04 cow kernel: usb 1-2: New USB device found, idVendor=12d1, idProduct=1436 Aug  2 08:11:04 cow kernel: usb 1-2: New USB device strings: Mfr=4, Product=3, SerialNumber=0 Aug  2 08:11:04 cow kernel: usb 1-2: Product: HUAWEI Mobile Aug  2 08:11:04 cow kernel: usb 1-2: Manufacturer: HUAWEI Technology Aug  2 08:11:04 cow kernel: usb-storage 1-2:1.0: USB Mass Storage device detected Aug  2 08:11:04 cow kernel: option 1-2:1.0: GSM modem (1-port) converter detected Aug  2 08:11:04 cow kernel: usb 1-2: GSM modem (1-port) converter now attached to ttyUSB0 Aug  2 08:11:04 cow kernel: usb-storage 1-2:1.1: USB Mass Storage device detected Aug  2 08:11:04 cow kernel: usb-storage 1-2:1.2: USB Mass Storage device detected Aug  2 08:11:04 cow kernel: usb-storage 1-2:1.3: USB Mass Storage device detected Aug  2 08:11:04 cow kernel: option 1-2:1.3: GSM modem (1-port) converter detected Aug  2 08:11:04 cow kernel: usb 1-2: GSM modem (1-port) converter now attached to ttyUSB1 Aug  2 08:11:04 cow kernel: usb-storage 1-2:1.4: USB Mass Storage device detected Aug  2 08:11:04 cow kernel: option 1-2:1.4: GSM modem (1-port) converter detected Aug  2 08:11:04 cow kernel: usb 1-2: GSM modem (1-port) converter now attached to ttyUSB2 Aug  2 08:11:04 cow kernel: usb-storage 1-2:1.5: USB Mass Storage device detected Aug  2 08:11:04 cow kernel: scsi host20: usb-storage 1-2:1.5 Aug  2 08:11:04 cow kernel: usb-storage 1-2:1.6: USB Mass Storage device detected Aug  2 08:11:04 cow kernel: scsi host21: usb-storage 1-2:1.6 Aug  2 08:11:02 cow ModemManager[2800]: <warn>  (ttyUSB1): port attributes not fully set Aug  2 08:11:03 cow ModemManager[2800]: <warn>  (ttyUSB2): port attributes not fully set Aug  2 08:11:03 cow laptop-mode[6377]: Laptop mode Aug  2 08:11:03 cow laptop-mode[6378]: enabled, not active Aug  2 08:11:03 cow laptop-mode[6410]: Laptop mode Aug  2 08:11:03 cow laptop-mode[6411]: enabled, not active Aug  2 08:11:03 cow logger[6429]: usb_modeswitch: switched to 12d1:1436 on 001/009 Aug  2 08:11:04 cow ModemManager[2800]: <warn>  (ttyUSB0): port attributes not fully set Aug  2 08:11:04 cow laptop-mode[6474]: Laptop mode Aug  2 08:11:04 cow laptop-mode[6475]: enabled, not active Aug  2 08:11:06 cow ModemManager[2800]: <warn>  (ttyUSB1): port attributes not fully set Aug  2 08:11:06 cow ModemManager[2800]: <warn>  (ttyUSB2): port attributes not fully set Aug  2 08:11:10 cow kernel: scsi 20:0:0:0: CD-ROM            HUAWEI   Mass Storage     2.31 PQ: 0 ANSI: 2 Aug  2 08:11:10 cow kernel: scsi 21:0:0:0: Direct-Access     HUAWEI   SD Storage       2.31 PQ: 0 ANSI: 2 Aug  2 08:11:10 cow kernel: sd 21:0:0:0: Attached scsi generic sg1 type 0 Aug  2 08:11:10 cow kernel: sr 20:0:0:0: [sr0] scsi-1 drive Aug  2 08:11:10 cow kernel: sr 20:0:0:0: Attached scsi CD-ROM sr0 Aug  2 08:11:10 cow kernel: sr 20:0:0:0: Attached scsi generic sg2 type 5 Aug  2 08:11:10 cow kernel: sd 21:0:0:0: [sdb] Attached SCSI removable disk Aug  2 08:11:15 cow ModemManager[2800]: <info>  Creating modem with plugin 'Huawei' and '3' ports Aug  2 08:11:15 cow ModemManager[2800]: <warn>  (ttyUSB2): port attributes not fully set Aug  2 08:11:15 cow ModemManager[2800]: <info>  Modem for device at '/sys/devices/pci0000:00/0000:00:14.0/usb1/1-2' successfully created Aug  2 08:11:16 cow ModemManager[2800]: Error while checking ^SYSCFGEX format: Unknown error Aug  2 08:11:16 cow ModemManager[2800]: <warn>  couldn't load Supported IP families: 'SIM PIN required' Aug  2 08:11:16 cow ModemManager[2800]: <info>  Modem: state changed (unknown -> locked) Aug  2 08:11:16 cow ModemManager[2800]: <warn>  couldn't load IMSI: 'SIM PIN required' Aug  2 08:11:16 cow ModemManager[2800]: <warn>  couldn't load Operator identifier: 'Cannot load Operator ID without IMSI' Aug  2 08:11:16 cow ModemManager[2800]: <warn>  couldn't load list of Own Numbers: 'Failed to parse NV MDN command result: -17' Aug  2 08:11:16 cow NetworkManager[5227]: <warn>  (ttyUSB2): cannot enable/disable modem: locked Aug  2 08:11:16 cow NetworkManager[5227]: <info>  (ttyUSB2): new Broadband device (driver: 'option1' ifindex: 0) Aug  2 08:11:16 cow NetworkManager[5227]: <info>  (ttyUSB2): exported as /org/freedesktop/NetworkManager/Devices/6 Aug  2 08:11:16 cow NetworkManager[5227]: <info>  (ttyUSB2): device state change: unmanaged -> unavailable (reason 'managed') [10 20 2] Aug  2 08:11:16 cow NetworkManager[5227]: <info>  (ttyUSB2): preparing device Aug  2 08:11:16 cow NetworkManager[5227]: <info>  (ttyUSB2): modem state 'locked' Aug  2 08:11:16 cow NetworkManager[5227]: <info>  (ttyUSB2): device state change: unavailable -> disconnected (reason 'none') [20 30 0] Aug  2 08:11:16 cow ModemManager[2800]: <warn>  (ttyUSB2): port attributes not fully set Aug  2 08:11:16 cow ModemManager[2800]: <warn>  (ttyUSB2): port attributes not fully set Aug  2 08:11:19 cow ModemManager[2800]: <info>  Modem /org/freedesktop/ModemManager1/Modem/1: state changed (locked -> initializing) Aug  2 08:11:19 cow ModemManager[2800]: <warn>  (ttyUSB2): port attributes not fully set Aug  2 08:11:20 cow ModemManager[2800]: <info>  Modem /org/freedesktop/ModemManager1/Modem/1: state changed (initializing -> disabled) Aug  2 08:11:20 cow NetworkManager[5227]: <info>  (ttyUSB2): modem state changed, 'locked' --> 'disabled' (reason: unknown) Aug  2 08:11:20 cow NetworkManager[5227]: <info>  (ttyUSB2): modem state changed, 'disabled' --> 'enabling' (reason: user preference) Aug  2 08:11:20 cow ModemManager[2800]: <info>  Modem /org/freedesktop/ModemManager1/Modem/1: state changed (disabled -> enabling) Aug  2 08:11:20 cow ModemManager[2800]: <warn>  (ttyUSB2): port attributes not fully set Aug  2 08:11:21 cow ModemManager[2800]: <info>  Modem /org/freedesktop/ModemManager1/Modem/1: 3GPP Registration state changed (unknown -> registering) Aug  2 08:11:21 cow ModemManager[2800]: <info>  Modem /org/freedesktop/ModemManager1/Modem/1: 3GPP Registration state changed (registering -> home) Aug  2 08:11:21 cow ModemManager[2800]: <info>  Modem /org/freedesktop/ModemManager1/Modem/1: state changed (enabling -> registered) Aug  2 08:11:21 cow NetworkManager[5227]: <info>  (ttyUSB2): modem state changed, 'enabling' --> 'registered' (reason: user-requested)

   
   
4. try to connect to preconfigured mobile broadband network with NetworkManager (via nm-applet) => connection fails
   

   Code:

   Aug  2 08:12:55 cow NetworkManager[5227]: <info>  (ttyUSB2): Activation: starting connection 'O2 Pay-by-MB' Aug  2 08:12:55 cow NetworkManager[5227]: <info>  (ttyUSB2): Activation: Stage 1 of 5 (Device Prepare) scheduled... Aug  2 08:12:55 cow NetworkManager[5227]: <info>  (ttyUSB2): Activation: Stage 1 of 5 (Device Prepare) started... Aug  2 08:12:55 cow NetworkManager[5227]: <info>  (ttyUSB2): device state change: disconnected -> prepare (reason 'none') [30 40 0] Aug  2 08:12:55 cow NetworkManager[5227]: <info>  NetworkManager state is now CONNECTING Aug  2 08:12:55 cow NetworkManager[5227]: <warn>  (ttyUSB2): Failed to connect 'O2 Pay-by-MB': Connection requested IPv4 but IPv4 is unsuported by the modem. Aug  2 08:12:55 cow NetworkManager[5227]: <info>  (ttyUSB2): device state change: prepare -> failed (reason 'modem-init-failed') [40 120 28] Aug  2 08:12:55 cow NetworkManager[5227]: <info>  NetworkManager state is now DISCONNECTED Aug  2 08:12:55 cow NetworkManager[5227]: <warn>  (ttyUSB2): Activation: failed for connection 'O2 Pay-by-MB' Aug  2 08:12:55 cow NetworkManager[5227]: <info>  (ttyUSB2): Activation: Stage 1 of 5 (Device Prepare) complete. Aug  2 08:12:55 cow NetworkManager[5227]: <info>  (ttyUSB2): device state change: failed -> disconnected (reason 'none') [120 30 0] Aug  2 08:12:55 cow NetworkManager[5227]: <info>  (ttyUSB2): deactivating device (reason 'none') [0]

   
   
5. restart NetworkManager (/etc/init.d/NetworkManager restart; the USB dongle stays plugged in)
   

   Code:

   Aug  2 08:13:35 cow NetworkManager[5227]: <info>  caught signal 15, shutting down normally. Aug  2 08:13:35 cow NetworkManager[5227]: <info>  (enp3s0): device state change: unavailable -> unmanaged (reason 'unmanaged') [20 10 3] Aug  2 08:13:37 cow kernel: IPv6: ADDRCONF(NETDEV_UP): enp3s0: link is not ready Aug  2 08:13:36 cow NetworkManager[5227]: <info>  (wlp4s0): device state change: disconnected -> unmanaged (reason 'unmanaged') [30 10 3] Aug  2 08:13:37 cow kernel: IPv6: ADDRCONF(NETDEV_UP): wlp4s0: link is not ready Aug  2 08:13:36 cow NetworkManager[5227]: <info>  (ttyUSB2): device state change: disconnected -> unmanaged (reason 'unmanaged') [30 10 3] Aug  2 08:13:36 cow NetworkManager[5227]: <info>  exiting (success) Aug  2 08:13:36 cow NetworkManager[6585]: <info>  NetworkManager (version 1.0.2) is starting... Aug  2 08:13:36 cow NetworkManager[6585]: <info>  Read config: /etc/NetworkManager/NetworkManager.conf Aug  2 08:13:36 cow NetworkManager[6585]: <info>  WEXT support is disabled Aug  2 08:13:36 cow NetworkManager[6585]: <info>  VPN: loaded org.freedesktop.NetworkManager.vpnc Aug  2 08:13:36 cow NetworkManager[6585]: <info>  VPN: loaded org.freedesktop.NetworkManager.openvpn Aug  2 08:13:36 cow NetworkManager[6585]: <info>  VPN: loaded org.freedesktop.NetworkManager.openconnect Aug  2 08:13:36 cow NetworkManager[6585]: <info>  Loaded plugin keyfile: (c) 2007 - 2015 Red Hat, Inc.  To report bugs please use the NetworkManager mailing list. Aug  2 08:13:36 cow NetworkManager[6585]: <info>  keyfile: new connection /etc/NetworkManager/system-connections/bom (########-####-####-####-############,"bom") Aug  2 08:13:36 cow NetworkManager[6585]: <info>  keyfile: new connection /etc/NetworkManager/system-connections/bar (########-####-####-####-############,"bar") Aug  2 08:13:36 cow NetworkManager[6585]: <info>  keyfile: new connection /etc/NetworkManager/system-connections/O2 Pay-by-MB (61f8c610-c549-45e6-82e6-044c6f77e35d,"O2 Pay-by-MB") Aug  2 08:13:36 cow NetworkManager[6585]: <info>  keyfile: new connection /etc/NetworkManager/system-connections/baz (########-####-####-####-############,"baz") Aug  2 08:13:36 cow NetworkManager[6585]: <info>  keyfile: new connection /etc/NetworkManager/system-connections/bat (########-####-####-####-############,"bat") Aug  2 08:13:36 cow NetworkManager[6585]: <warn>  keyfile: error loading connection from file /etc/NetworkManager/system-connections/.keep_net-misc_networkmanager-0: invalid connection: connection.type: property is missing Aug  2 08:13:36 cow NetworkManager[6585]: <info>  keyfile: new connection /etc/NetworkManager/system-connections/bar (########-####-####-####-############,"bar") Aug  2 08:13:36 cow NetworkManager[6585]: <info>  keyfile: new connection /etc/NetworkManager/system-connections/foo (########-####-####-####-############,"foo") Aug  2 08:13:36 cow NetworkManager[6585]: <info>  monitoring kernel firmware directory '/lib/firmware'. Aug  2 08:13:36 cow NetworkManager[6585]: <info>  rfkill1: found WiFi radio killswitch (at /sys/devices/pci0000:00/0000:00:1c.2/0000:04:00.0/ieee80211/phy0/rfkill1) (driver iwlwifi) Aug  2 08:13:36 cow NetworkManager[6585]: <info>  WiFi hardware radio set enabled Aug  2 08:13:36 cow NetworkManager[6585]: <info>  WWAN hardware radio set enabled Aug  2 08:13:36 cow NetworkManager[6585]: <info>  Loaded device plugin: /usr/lib64/NetworkManager/libnm-device-plugin-bluetooth.so Aug  2 08:13:36 cow NetworkManager[6585]: <info>  Loaded device plugin: /usr/lib64/NetworkManager/libnm-device-plugin-wifi.so Aug  2 08:13:36 cow NetworkManager[6585]: <info>  Loaded device plugin: /usr/lib64/NetworkManager/libnm-device-plugin-adsl.so Aug  2 08:13:36 cow NetworkManager[6585]: <info>  Loaded device plugin: /usr/lib64/NetworkManager/libnm-device-plugin-wwan.so Aug  2 08:13:36 cow NetworkManager[6585]: <info>  WiFi enabled by radio killswitch; enabled by state file Aug  2 08:13:36 cow NetworkManager[6585]: <info>  WWAN enabled by radio killswitch; enabled by state file Aug  2 08:13:36 cow NetworkManager[6585]: <info>  WiMAX enabled by radio killswitch; enabled by state file Aug  2 08:13:36 cow NetworkManager[6585]: <info>  Networking is enabled by state file Aug  2 08:13:36 cow NetworkManager[6585]: <info>  (lo): link connected Aug  2 08:13:36 cow NetworkManager[6585]: <info>  (lo): carrier is ON Aug  2 08:13:36 cow NetworkManager[6585]: <info>  (lo): new Generic device (driver: 'unknown' ifindex: 1) Aug  2 08:13:36 cow NetworkManager[6585]: <info>  (lo): exported as /org/freedesktop/NetworkManager/Devices/0 Aug  2 08:13:36 cow NetworkManager[6585]: <info>  (enp3s0): carrier is OFF Aug  2 08:13:36 cow NetworkManager[6585]: <info>  (enp3s0): new Ethernet device (driver: 'r8169' ifindex: 2) Aug  2 08:13:36 cow NetworkManager[6585]: <info>  (enp3s0): exported as /org/freedesktop/NetworkManager/Devices/1 Aug  2 08:13:36 cow NetworkManager[6585]: <info>  (enp3s0): device state change: unmanaged -> unavailable (reason 'managed') [10 20 2] Aug  2 08:13:36 cow NetworkManager[6585]: <info>  (enp3s0): preparing device Aug  2 08:13:37 cow kernel: r8169 0000:03:00.0 enp3s0: link down Aug  2 08:13:36 cow NetworkManager[6585]: <info>  (sit0): new Generic device (driver: 'sit' ifindex: 3) Aug  2 08:13:36 cow NetworkManager[6585]: <info>  (sit0): exported as /org/freedesktop/NetworkManager/Devices/2 Aug  2 08:13:36 cow NetworkManager[6585]: <info>  (wlp4s0): using nl80211 for WiFi device control Aug  2 08:13:36 cow NetworkManager[6585]: <info>  (wlp4s0): driver supports Access Point (AP) mode Aug  2 08:13:36 cow NetworkManager[6585]: <info>  (wlp4s0): new 802.11 WiFi device (driver: 'iwlwifi' ifindex: 4) Aug  2 08:13:36 cow NetworkManager[6585]: <info>  (wlp4s0): exported as /org/freedesktop/NetworkManager/Devices/3 Aug  2 08:13:36 cow NetworkManager[6585]: <info>  (wlp4s0): device state change: unmanaged -> unavailable (reason 'managed') [10 20 2] Aug  2 08:13:38 cow kernel: iwlwifi 0000:04:00.0: L1 Enabled - LTR Enabled Aug  2 08:13:38 cow kernel: iwlwifi 0000:04:00.0: L1 Enabled - LTR Enabled Aug  2 08:13:36 cow NetworkManager[6585]: <info>  (wlp4s0): preparing device Aug  2 08:13:36 cow NetworkManager[6585]: <info>  (wlp4s0) supports 5 scan SSIDs Aug  2 08:13:36 cow NetworkManager[6585]: <info>  (wlp4s0): supplicant interface state: starting -> ready Aug  2 08:13:36 cow NetworkManager[6585]: <info>  (wlp4s0): device state change: unavailable -> disconnected (reason 'supplicant-available') [20 30 42] Aug  2 08:13:36 cow NetworkManager[6585]: <info>  ModemManager available in the bus Aug  2 08:13:36 cow NetworkManager[6585]: <info>  (ttyUSB2): new Broadband device (driver: 'option1' ifindex: 0) Aug  2 08:13:36 cow NetworkManager[6585]: <info>  (ttyUSB2): exported as /org/freedesktop/NetworkManager/Devices/4 Aug  2 08:13:36 cow NetworkManager[6585]: <info>  (ttyUSB2): device state change: unmanaged -> unavailable (reason 'managed') [10 20 2] Aug  2 08:13:36 cow NetworkManager[6585]: <info>  (ttyUSB2): preparing device Aug  2 08:13:36 cow NetworkManager[6585]: <info>  (ttyUSB2): modem state 'registered' Aug  2 08:13:36 cow NetworkManager[6585]: <info>  (wlp4s0): supplicant interface state: ready -> disconnected Aug  2 08:13:36 cow NetworkManager[6585]: <info>  (wlp4s0) supports 5 scan SSIDs Aug  2 08:13:36 cow NetworkManager[6585]: <info>  (ttyUSB2): device state change: unavailable -> disconnected (reason 'none') [20 30 0] Aug  2 08:13:37 cow /etc/init.d/NetworkManager[6547]: WARNING: NetworkManager has started, but is inactive Aug  2 08:13:39 cow NetworkManager[6585]: <info>  (wlp4s0): supplicant interface state: disconnected -> inactive Aug  2 08:13:41 cow NetworkManager[6585]: <info>  startup complete

   
   
6. try to connect to preconfigured mobile broadband network with NetworkManager (via nm-applet) => success (can browse web, etc.)
   

   Code:

   Aug  2 08:13:58 cow NetworkManager[6585]: <info>  (ttyUSB2): Activation: starting connection 'O2 Pay-by-MB' Aug  2 08:13:58 cow NetworkManager[6585]: <info>  (ttyUSB2): Activation: Stage 1 of 5 (Device Prepare) scheduled... Aug  2 08:13:58 cow NetworkManager[6585]: <info>  (ttyUSB2): Activation: Stage 1 of 5 (Device Prepare) started... Aug  2 08:13:58 cow NetworkManager[6585]: <info>  (ttyUSB2): device state change: disconnected -> prepare (reason 'none') [30 40 0] Aug  2 08:13:58 cow NetworkManager[6585]: <info>  NetworkManager state is now CONNECTING Aug  2 08:13:58 cow NetworkManager[6585]: <info>  (ttyUSB2): Activation: Stage 1 of 5 (Device Prepare) complete. Aug  2 08:13:58 cow ModemManager[2800]: <info>  Simple connect started... Aug  2 08:13:58 cow ModemManager[2800]: <info>  Simple connect state (4/8): Wait to get fully enabled Aug  2 08:13:58 cow ModemManager[2800]: <info>  Simple connect state (5/8): Register Aug  2 08:13:58 cow ModemManager[2800]: <info>  Simple connect state (6/8): Bearer Aug  2 08:13:58 cow ModemManager[2800]: <info>  Simple connect state (7/8): Connect Aug  2 08:13:58 cow ModemManager[2800]: <info>  Modem /org/freedesktop/ModemManager1/Modem/1: state changed (registered -> connecting) Aug  2 08:13:58 cow NetworkManager[6585]: <info>  (ttyUSB2): modem state changed, 'registered' --> 'connecting' (reason: user-requested) Aug  2 08:13:58 cow ModemManager[2800]: <warn>  (ttyUSB0): port attributes not fully set Aug  2 08:13:58 cow ModemManager[2800]: <info>  Modem /org/freedesktop/ModemManager1/Modem/1: state changed (connecting -> connected) Aug  2 08:13:58 cow ModemManager[2800]: <info>  Simple connect state (8/8): All done Aug  2 08:13:58 cow NetworkManager[6585]: <info>  (ttyUSB2): modem state changed, 'connecting' --> 'connected' (reason: user-requested) Aug  2 08:13:58 cow NetworkManager[6585]: <warn>  (ttyUSB2): failed to look up interface index Aug  2 08:13:58 cow NetworkManager[6585]: <info>  (ttyUSB2): Activation: Stage 2 of 5 (Device Configure) scheduled... Aug  2 08:13:58 cow NetworkManager[6585]: <info>  (ttyUSB2): Activation: Stage 2 of 5 (Device Configure) starting... Aug  2 08:13:58 cow NetworkManager[6585]: <info>  (ttyUSB2): device state change: prepare -> config (reason 'none') [40 50 0] Aug  2 08:13:58 cow NetworkManager[6585]: <info>  (ttyUSB2): Activation: Stage 2 of 5 (Device Configure) successful. Aug  2 08:13:58 cow NetworkManager[6585]: <info>  (ttyUSB2): Activation: Stage 2 of 5 (Device Configure) complete. Aug  2 08:13:58 cow NetworkManager[6585]: <info>  (ttyUSB2): Activation: Stage 3 of 5 (IP Configure Start) scheduled. Aug  2 08:13:58 cow NetworkManager[6585]: <info>  (ttyUSB2): Activation: Stage 3 of 5 (IP Configure Start) started... Aug  2 08:13:58 cow NetworkManager[6585]: <info>  (ttyUSB2): device state change: config -> ip-config (reason 'none') [50 70 0] Aug  2 08:13:58 cow NetworkManager[6585]: <warn>  (ttyUSB2): interface ttyUSB0 not up for IP configuration Aug  2 08:13:58 cow NetworkManager[6585]: <info>  (ttyUSB2): using modem-specified IP timeout: 20 seconds Aug  2 08:13:58 cow NetworkManager[6585]: <info>  starting PPP connection Aug  2 08:13:58 cow NetworkManager[6585]: <info>  pppd started with pid 6623 Aug  2 08:13:58 cow NetworkManager[6585]: <info>  (ttyUSB2): Activation: Stage 3 of 5 (IP Configure Start) complete. Aug  2 08:13:58 cow pppd[6623]: Plugin /usr/lib64/pppd/2.4.7/nm-pppd-plugin.so loaded. Aug  2 08:13:58 cow pppd[6623]: pppd 2.4.7 started by larry, uid 0 Aug  2 08:13:58 cow pppd[6623]: Using interface ppp0 Aug  2 08:13:58 cow pppd[6623]: Connect: ppp0 <--> /dev/ttyUSB0 Aug  2 08:13:58 cow NetworkManager[6585]: <info>  (ppp0): new Generic device (driver: 'unknown' ifindex: 6) Aug  2 08:13:58 cow NetworkManager[6585]: <info>  (ppp0): exported as /org/freedesktop/NetworkManager/Devices/5 Aug  2 08:13:58 cow pppd[6623]: CHAP authentication succeeded Aug  2 08:13:58 cow pppd[6623]: CHAP authentication succeeded Aug  2 08:14:01 cow pppd[6623]: Could not determine remote IP address: defaulting to 10.##.##.## Aug  2 08:14:01 cow pppd[6623]: local  IP address 10.##.##.## Aug  2 08:14:01 cow pppd[6623]: remote IP address 10.##.##.## Aug  2 08:14:01 cow pppd[6623]: primary   DNS address ###.###.###.### Aug  2 08:14:01 cow pppd[6623]: secondary DNS address ###.###.###.### Aug  2 08:14:01 cow NetworkManager[6585]: <info>  PPP manager (IPv4 Config Get) reply received. Aug  2 08:14:01 cow NetworkManager[6585]: <info>  (ttyUSB2): Activation: Stage 5 of 5 (IPv4 Configure Commit) scheduled... Aug  2 08:14:01 cow NetworkManager[6585]: <info>  (ttyUSB2): Activation: Stage 5 of 5 (IPv4 Commit) started... Aug  2 08:14:01 cow NetworkManager[6585]: <info>  (ttyUSB2): device state change: ip-config -> ip-check (reason 'none') [70 80 0] Aug  2 08:14:01 cow NetworkManager[6585]: <info>  (ttyUSB2): Activation: Stage 5 of 5 (IPv4 Commit) complete. Aug  2 08:14:01 cow NetworkManager[6585]: <info>  (ttyUSB2): device state change: ip-check -> secondaries (reason 'none') [80 90 0] Aug  2 08:14:01 cow NetworkManager[6585]: <info>  (ttyUSB2): device state change: secondaries -> activated (reason 'none') [90 100 0] Aug  2 08:14:01 cow NetworkManager[6585]: <info>  NetworkManager state is now CONNECTED_LOCAL Aug  2 08:14:01 cow NetworkManager[6585]: <info>  NetworkManager state is now CONNECTED_GLOBAL Aug  2 08:14:01 cow NetworkManager[6585]: <info>  Policy set 'O2 Pay-by-MB' (ppp0) as default for IPv4 routing and DNS. Aug  2 08:14:01 cow NetworkManager[6585]: <info>  (ttyUSB2): Activation: successful, device activated. Aug  2 08:14:01 cow dbus[2767]: [system] Activating service name='org.freedesktop.nm_dispatcher' (using servicehelper) Aug  2 08:14:01 cow dbus[2767]: [system] Successfully activated service 'org.freedesktop.nm_dispatcher' Aug  2 08:14:01 cow nm-dispatcher[6644]: Dispatching action 'up' for ppp0 Aug  2 08:14:01 cow /etc/init.d/NetworkManager[6657]: status: inactive Aug  2 08:14:01 cow /etc/init.d/NetworkManager[6669]: status: inactive

   
   

Conclusion/Question:
I researched the error messages and always ended up with inconclusive results.
I have not been able to determine the root of the problem and would be grateful for any help in doing so in order to finally solve my problem.

Thank you very much for your advice in advance.