service NetworkManager status
У меня такая же проблема. Помогает вытаскивание модема и выход-вход с пользовательской сессии. Или загрузка без модема, а только потом его вставка в порт.
Вот вывод моей команды 'systemctl status NetworkManager.service | less'
NetworkManager.service - Network Manager
Loaded: loaded (/lib/systemd/system/NetworkManager.service; enabled)
Active: active (running) since Вт 2014-11-04 09:12:21 MSK; 9min ago
Process: 15919 ExecStartPre=/usr/sbin/NetworkManager-prestart (code=exited, status=0/SUCCESS)
Main PID: 15934 (NetworkManager)
CGroup: name=systemd:/system/NetworkManager.service
├─15934 /usr/sbin/NetworkManager --no-daemon
└─16983 /usr/sbin/pppd nodetach lock nodefaultroute ipv6 , ttyUSB0 noipdefault noauth usepeerdns lcp-echo-failure 5 lcp-echo-interval 30 ipparam /org/freedesktop/NetworkManager/PPP/0 plugin /usr/lib/pppd/2.4.5/nm-pppd-plugin.so
ноя 04 09:16:10 homezevs.localdomain NetworkManager[15934]: Connect: ppp0 <--> /dev/ttyUSB0
ноя 04 09:16:10 homezevs.localdomain NetworkManager[15934]: CHAP authentication succeeded
ноя 04 09:16:10 homezevs.localdomain NetworkManager[15934]: CHAP authentication succeeded
ноя 04 09:16:12 homezevs.localdomain NetworkManager[15934]: Could not determine remote IP address: defaulting to 10.64.64.64
ноя 04 09:16:12 homezevs.localdomain NetworkManager[15934]: local IP address 10.209.*.*
ноя 04 09:16:12 homezevs.localdomain NetworkManager[15934]: remote IP address 10.64.64.64
ноя 04 09:16:12 homezevs.localdomain NetworkManager[15934]: primary DNS address 10.163.182.11
ноя 04 09:16:12 homezevs.localdomain NetworkManager[15934]: secondary DNS address 10.163.182.10
ноя 04 09:16:24 homezevs.localdomain NetworkManager[15934]: Script /etc/ppp/ip-up finished (pid 16998), status = 0x0
ноя 04 09:16:40 homezevs.localdomain NetworkManager[15934]: IPV6CP: timeout sending Config-Requests