What is purpose of virbr0 interface

[kriticar]

I have installed centos 7, server with gui option. I don't remember that I turned on any kind of virtualisation.
Latter, I have noticed that virbr0 interface has showed.
What is the purpose of virbr0 interface, do I need it, and if not, how can I disable it?

[avij]

That is indeed related to virtualization. I'm not sure about this, but my best guess for disabling virbr0 is to run systemctl stop libvirtd.service, which will stop the virtualization service. If this helped, systemctl disable libvirtd.service will disable the service permanently.

[TrevorH]

The default desktop install includes gnome-boxes (possibly just 'boxes') which is a form of virt that uses libvirt. Uninstalling it should fix it too.

[kriticar]

If I execute

systemctl disable libvirtd.service

will I be able latter to enable the service with

systemctl disable libvirtd.service

in case I need it?

[avij]

I suppose you meant systemctl enable libvirtd.service, but yeah, that will re-enable the service the next time you reboot. To start the service without rebooting, you can use systemctl start libvirtd.service, but that won't be a permanent change.

[kriticar]

Thank you very very much.

[jlehtone]

The default desktop install includes gnome-boxes (possibly just 'boxes') which is a form of virt that uses libvirt. Uninstalling it should fix it too.

Ahh, gnome-boxes requires libvirt.

Libvirt, if installed, has libvirtd.service enabled by default.
Libvirt has a network definition "default" preconfigured and set to autostart.
The "virbr0" is a bridge interface that represents a network (a bridge is essentially a network switch).

Therefore, by installing libvirt (for any reason) by default dynamically creates the "virbr0" on every boot (and adds some netfilter rules too).

One can disable the autostart of the default network.
One can remove the definition of the default network.
One can stop and disable the libvirtd.service.
One can uninstall the libvirt packages.

[MartinR]

This may be of interest. It is meant to be conceptual rather than a detailed analysis.

Virbr-NAT.gif