It seems the 15.04 version of network manager (0.9.10) is now quite out-of-date (!).
https://wiki.gnome.org/Projects/NetworkManager/
From https://download.gnome.org/sources/NetworkManager/1.0/NetworkManager-1.0.4.news
* The management of devices can now be controlled with udev rules. The veth devices as well as the virtual Ethernet devices of various virtualization tools (VMWare, VirtualBox, Parallels Workstation) are now ignored by default.
It seems the 15.04 version of network manager (0.9.10) is now quite out-of-date (!).
https:/ /wiki.gnome. org/Projects/ NetworkManager/
From https:/ /download. gnome.org/ sources/ NetworkManager/ 1.0/NetworkMana ger-1.0. 4.news
* The management of devices can now be controlled with udev rules. The veth
devices as well as the virtual Ethernet devices of various
virtualization tools (VMWare, VirtualBox, Parallels Workstation) are
now ignored by default.