Comment 38 for bug 1432599

In previous versions of GNOME (such as the version in RHEL 7.6), an active NetworkManager connection profile for virbr0 caused a wired Ethernet connection to appear in the top bar in GNOME Shell. It seems this is actually now suppressed, and GNOME Control Center does not expose the virbr0 device on the network panel (or allow it to be configured there).

For users who are looking to check if a NetworkManager connection profile is active excluding libvirt's, disabling NetworkManager's control of the bridge devices still seems to me like an appropriate method to adjust the behavior of nm-online. I'm not sure I agree with the comment about *never* using ifcfg: the configuration I provided above is equivalent to setting "unmanaged-devices=interface-name:virbr0" in /etc/NetworkManager/NetworkManager.conf. It is read by NetworkManager's ifcfg-rh settings plugin, versus NetworkManager's keyfile settings plugin.

It's also worth mentioning that libvirt allows hook scripts to be run when a virtual network switch is started/stopped, which can substitute for NetworkManager dispatcher scripts for these devices: https://libvirt.org/hooks.html