então a questão é basicamente que qualquer tentativa de conexão com a VPN do meu escritório falha no Ubuntu 14.04.
Não há configurações especiais, mas vale a pena mencionar que é para o PPTP.
Eu posso fazer ping no servidor com bastante facilidade. Não tenho certeza de que tipo de informação eu posso colocar aqui para tornar isso mais diagnosticável, mas por favor me avise.
A saída é a seguinte:
Sep 29 17:24:27 pedri-home NetworkManager[912]: <info> Starting VPN service 'pptp'...
Sep 29 17:24:27 pedri-home NetworkManager[912]: <info> VPN service 'pptp' started (org.freedesktop.NetworkManager.pptp), PID 18760
Sep 29 17:24:27 pedri-home NetworkManager[912]: <info> VPN service 'pptp' appeared; activating connections
Sep 29 17:24:27 pedri-home NetworkManager[912]: <info> VPN plugin state changed: init (1)
Sep 29 17:24:27 pedri-home NetworkManager[912]: <info> VPN plugin state changed: starting (3)
Sep 29 17:24:27 pedri-home pppd[18764]: Plugin /usr/lib/pppd/2.4.5/nm-pptp-pppd-plugin.so loaded.
Sep 29 17:24:27 pedri-home NetworkManager[912]: <info> VPN connection 'Test2' (Connect) reply received.
Sep 29 17:24:27 pedri-home pppd[18764]: pppd 2.4.5 started by root, uid 0
Sep 29 17:24:27 pedri-home pppd[18764]: Using interface ppp0
Sep 29 17:24:27 pedri-home pppd[18764]: Connect: ppp0 <--> /dev/pts/26
Sep 29 17:24:27 pedri-home pptp[18767]: nm-pptp-service-18760 log[main:pptp.c:314]: The synchronous pptp option is NOT activated
Sep 29 17:24:27 pedri-home NetworkManager[912]: SCPlugin-Ifupdown: devices added (path: /sys/devices/virtual/net/ppp0, iface: ppp0)
Sep 29 17:24:27 pedri-home NetworkManager[912]: SCPlugin-Ifupdown: device added (path: /sys/devices/virtual/net/ppp0, iface: ppp0): no ifupdown configuration found.
Sep 29 17:24:27 pedri-home NetworkManager[912]: <warn> /sys/devices/virtual/net/ppp0: couldn't determine device driver; ignoring...
Sep 29 17:24:28 pedri-home pptp[18780]: nm-pptp-service-18760 log[ctrlp_rep:pptp_ctrl.c:251]: Sent control packet type is 1 'Start-Control-Connection-Request'
Sep 29 17:24:29 pedri-home pptp[18780]: nm-pptp-service-18760 log[ctrlp_disp:pptp_ctrl.c:739]: Received Start Control Connection Reply
Sep 29 17:24:29 pedri-home pptp[18780]: nm-pptp-service-18760 log[ctrlp_disp:pptp_ctrl.c:773]: Client connection established.
Sep 29 17:24:29 pedri-home pptp[18780]: nm-pptp-service-18760 log[ctrlp_rep:pptp_ctrl.c:251]: Sent control packet type is 7 'Outgoing-Call-Request'
Sep 29 17:24:29 pedri-home pptp[18780]: nm-pptp-service-18760 log[ctrlp_disp:pptp_ctrl.c:858]: Received Outgoing Call Reply.
Sep 29 17:24:29 pedri-home pptp[18780]: nm-pptp-service-18760 log[ctrlp_disp:pptp_ctrl.c:897]: Outgoing call established (call ID 0, peer's call ID 150).
Sep 29 17:24:58 pedri-home pppd[18764]: LCP: timeout sending Config-Requests
Sep 29 17:24:58 pedri-home pppd[18764]: Connection terminated.
Sep 29 17:24:58 pedri-home NetworkManager[912]: <warn> VPN plugin failed: 1
Sep 29 17:24:58 pedri-home pppd[18764]: Modem hangup
Sep 29 17:24:58 pedri-home pptp[18767]: nm-pptp-service-18760 warn[decaps_hdlc:pptp_gre.c:204]: short read (-1): Input/output error
Sep 29 17:24:58 pedri-home pptp[18767]: nm-pptp-service-18760 warn[decaps_hdlc:pptp_gre.c:216]: pppd may have shutdown, see pppd log
Sep 29 17:24:58 pedri-home pppd[18764]: Exit.
Sep 29 17:24:58 pedri-home NetworkManager[912]: message repeated 2 times: [ <warn> VPN plugin failed: 1]
Sep 29 17:24:58 pedri-home NetworkManager[912]: <info> VPN plugin state changed: stopped (6)
Sep 29 17:24:58 pedri-home NetworkManager[912]: <info> VPN plugin state change reason: 0
Sep 29 17:24:58 pedri-home NetworkManager[912]: <info> Policy set 'Wired connection 1' (eth0) as default for IPv4 routing and DNS.
Sep 29 17:24:58 pedri-home pptp[18780]: nm-pptp-service-18760 log[callmgr_main:pptp_callmgr.c:234]: Closing connection (unhandled)
Sep 29 17:24:58 pedri-home pptp[18780]: nm-pptp-service-18760 log[ctrlp_rep:pptp_ctrl.c:251]: Sent control packet type is 12 'Call-Clear-Request'
Sep 29 17:24:58 pedri-home pptp[18780]: nm-pptp-service-18760 log[call_callback:pptp_callmgr.c:79]: Closing connection (call state)
Sep 29 17:24:58 pedri-home NetworkManager[912]: <warn> error disconnecting VPN: Could not process the request because no VPN connection was active.
Sep 29 17:24:58 pedri-home NetworkManager[912]: SCPlugin-Ifupdown: devices removed (path: /sys/devices/virtual/net/ppp0, iface: ppp0)
Sep 29 17:25:03 pedri-home NetworkManager[912]: <info> VPN service 'pptp' disappeared
Eu tive problemas semelhantes ao tentar configurar uma VPN sobre minha conexão ADSL doméstica. Uma coisa com a qual tive algum sucesso foi mudar o MTU na conexão PPPoE para Manual e configurá-lo em 1432. Ainda cai aleatoriamente de tempos em tempos, mas aguenta o tempo suficiente para fazer algum trabalho ...