maybe red herring, but see this entry which probably indicates that stuff doesn't go as expected:
Apr 28 16:55:42 ubuntu-phablet NetworkManager[1212]: <error> [1398718542.745922] [nm-system.c:965] add_ip4_route_to_gateway(): (rmnet_usb0): failed to add IPv4 route to gateway (-12) -- You received this bug notification because you are a member of Ubuntu Bugs, which is subscribed to Ubuntu. https://bugs.launchpad.net/bugs/1307981 Title: [touch] randomly messed up routing with recent trusty images To manage notifications about this bug go to: https://bugs.launchpad.net/ubuntu/+source/network-manager/+bug/1307981/+subscriptions -- ubuntu-bugs mailing list ubuntu-bugs@lists.ubuntu.com https://lists.ubuntu.com/mailman/listinfo/ubuntu-bugs
