我在 Ubuntu 16.04 上配置 VPN 连接时遇到困难。
命令：journalctl -u NetworkManager.service给我这个：
Oct 21 12:10:40 drbrcho NetworkManager[913]: <info> [1477044640.2686] audit: op="connection-activate" uuid="04c6d3d5-8c5f-4ca1-8b58-df3e8a77f067" name="VPN connection 1" pid=1670 uid=1000 result="success"
Oct 21 12:10:40 drbrcho NetworkManager[913]: <info> [1477044640.2709] vpn-connection[0x16257a0,04c6d3d5-8c5f-4ca1-8b58-df3e8a77f067,"VPN connection 1",0]: Started the VPN service, PID 7807
Oct 21 12:10:40 drbrcho NetworkManager[913]: <info> [1477044640.2770] vpn-connection[0x16257a0,04c6d3d5-8c5f-4ca1-8b58-df3e8a77f067,"VPN connection 1",0]: Saw the service appear; activating connection
Oct 21 12:10:44 drbrcho NetworkManager[913]: <info> [1477044644.5269] keyfile: update /etc/NetworkManager/system-connections/VPN connection 1 (04c6d3d5-8c5f-4ca1-8b58-df3e8a77f067,"VPN connection 1")
Oct 21 12:10:44 drbrcho NetworkManager[913]: <info> [1477044644.5297] vpn-connection[0x16257a0,04c6d3d5-8c5f-4ca1-8b58-df3e8a77f067,"VPN connection 1",0]: VPN connection: (ConnectInteractive) reply received
Oct 21 12:10:44 drbrcho NetworkManager[913]: ** Message: pppd started with pid 7821
Oct 21 12:10:44 drbrcho NetworkManager[913]: <info> [1477044644.9450] vpn-connection[0x16257a0,04c6d3d5-8c5f-4ca1-8b58-df3e8a77f067,"VPN connection 1",0]: VPN plugin: state changed: starting (3)
Oct 21 12:10:44 drbrcho pppd[7821]: Plugin /usr/lib/pppd/2.4.7/nm-pptp-pppd-plugin.so loaded.
Oct 21 12:10:44 drbrcho NetworkManager[913]: Plugin /usr/lib/pppd/2.4.7/nm-pptp-pppd-plugin.so loaded.
Oct 21 12:10:44 drbrcho NetworkManager[913]: ** Message: nm-pptp-ppp-plugin: (plugin_init): initializing
Oct 21 12:10:44 drbrcho pppd[7821]: pppd 2.4.7 started by root, uid 0
Oct 21 12:10:44 drbrcho NetworkManager[913]: ** Message: nm-pptp-ppp-plugin: (nm_phasechange): status 3 / phase 'serial connection'
Oct 21 12:10:44 drbrcho pppd[7821]: Using interface ppp0
Oct 21 12:10:44 drbrcho NetworkManager[913]: Using interface ppp0
Oct 21 12:10:44 drbrcho NetworkManager[913]: Connect: ppp0 <--> /dev/pts/2
Oct 21 12:10:44 drbrcho NetworkManager[913]: ** Message: nm-pptp-ppp-plugin: (nm_phasechange): status 5 / phase 'establish'
Oct 21 12:10:44 drbrcho NetworkManager[913]: nm_device_get_device_type: assertion 'NM_IS_DEVICE (self)' failed
Oct 21 12:10:44 drbrcho pppd[7821]: Connect: ppp0 <--> /dev/pts/2
Oct 21 12:10:44 drbrcho NetworkManager[913]: <info> [1477044644.9504] manager: (ppp0): new Generic device (/org/freedesktop/NetworkManager/Devices/13)
Oct 21 12:10:44 drbrcho pptp[7826]: nm-pptp-service-7807 log[main:pptp.c:350]: The synchronous pptp option is NOT activated
Oct 21 12:10:44 drbrcho NetworkManager[913]: <info> [1477044644.9543] devices added (path: /sys/devices/virtual/net/ppp0, iface: ppp0)
Oct 21 12:10:44 drbrcho NetworkManager[913]: <info> [1477044644.9543] device added (path: /sys/devices/virtual/net/ppp0, iface: ppp0): no ifupdown configuration found.
Oct 21 12:11:15 drbrcho pppd[7821]: LCP: timeout sending Config-Requests
Oct 21 12:11:15 drbrcho NetworkManager[913]: LCP: timeout sending Config-Requests
Oct 21 12:11:15 drbrcho NetworkManager[913]: ** Message: nm-pptp-ppp-plugin: (nm_phasechange): status 11 / phase 'disconnect'
Oct 21 12:11:15 drbrcho NetworkManager[913]: Connection terminated.
Oct 21 12:11:15 drbrcho pppd[7821]: Connection terminated.
Oct 21 12:11:15 drbrcho NetworkManager[913]: ** Message: Terminated ppp daemon with PID 7821.
Oct 21 12:11:15 drbrcho NetworkManager[913]: <error> [1477044675.9797] platform-linux: do-change-link[14]: failure changing link: failure 19 (No such device)
Oct 21 12:11:15 drbrcho NetworkManager[913]: <warn> [1477044675.9798] device (ppp0): failed to disable userspace IPv6LL address handling
Oct 21 12:11:15 drbrcho NetworkManager[913]: <warn> [1477044675.9801] vpn-connection[0x16257a0,04c6d3d5-8c5f-4ca1-8b58-df3e8a77f067,"VPN connection 1",0]: VPN plugin: failed: connect-failed (1)
Oct 21 12:11:15 drbrcho NetworkManager[913]: <info> [1477044675.9801] vpn-connection[0x16257a0,04c6d3d5-8c5f-4ca1-8b58-df3e8a77f067,"VPN connection 1",0]: VPN plugin: state changed: stopping (5)
Oct 21 12:11:15 drbrcho NetworkManager[913]: <info> [1477044675.9808] vpn-connection[0x16257a0,04c6d3d5-8c5f-4ca1-8b58-df3e8a77f067,"VPN connection 1",0]: VPN plugin: state changed: stopped (6)
Oct 21 12:11:15 drbrcho NetworkManager[913]: <info> [1477044675.9827] vpn-connection[0x16257a0,04c6d3d5-8c5f-4ca1-8b58-df3e8a77f067,"VPN connection 1",0]: VPN plugin: state change reason: unknown (0)
Oct 21 12:11:15 drbrcho NetworkManager[913]: <info> [1477044675.9843] devices removed (path: /sys/devices/virtual/net/ppp0, iface: ppp0)
Oct 21 12:11:15 drbrcho NetworkManager[913]: <info> [1477044675.9843] vpn-connection[0x16257a0,04c6d3d5-8c5f-4ca1-8b58-df3e8a77f067,"VPN connection 1",0]: VPN service disappeared
Oct 21 12:11:16 drbrcho NetworkManager[913]: ** Message: nm-pptp-ppp-plugin: (nm_phasechange): status 1 / phase 'dead'
Oct 21 12:11:16 drbrcho NetworkManager[913]: Terminating on signal 15
Oct 21 12:11:16 drbrcho NetworkManager[913]: Child process /usr/sbin/pptp 93.184.205.16 --nolaunchpppd --loglevel 0 --logstring nm-pptp-service-7807 (pid 7824) terminated with signal 15
Oct 21 12:11:16 drbrcho NetworkManager[913]: Modem hangup
Oct 21 12:11:16 drbrcho NetworkManager[913]: ** Message: nm-pptp-ppp-plugin: (nm_exit_notify): cleaning up
我该如何继续？