libvirt users - Jan 2021 - relation between "virbr0" / "virbr0-nic" network interfaces

I am trying to understand KVM networking a little better and have noted
that the "virbr0" network interface (the default KVM bridge) comes
with
another device named "virbr0-nic".
The same kind of pair comes with each new bridge you may create via the
"virtual machine manager" (and assumingly other KVM tools alike)
Like "virbr1" comes in a pair with "virbr1-nic" (the *-nic
interface is
being created automatically (and I assume will disapear automatically if
you remove the parent interface)

Can anybody kindly explain how these pairs are related to each other
and/or work together?

thanks ... Gunnar

On Fri, Jan 01, 2021 at 10:24:41AM +0100, vrms wrote:
> I am trying to understand KVM networking a little better and have noted
> that the "virbr0" network interface (the default KVM bridge)
comes with
> another device named "virbr0-nic".
> The same kind of pair comes with each new bridge you may create via the
> "virtual machine manager" (and assumingly other KVM tools alike)
> Like "virbr1" comes in a pair with "virbr1-nic" (the
*-nic interface is
> being created automatically (and I assume will disapear automatically if
> you remove the parent interface)
> 
> Can anybody kindly explain how these pairs are related to each other
> and/or work together?
The "$FOO-nic"  device is a tap device created as a hack to force a
stable MAC address on the main bridge device due to bad kernel impl
of bridge device MAC address assignment.

We stopped creating the "$FOO-nic" device in libvirt 6.8.0 since the
kernel was long ago fixed.

Regards,
Daniel
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