libvirt users - May 2022 - macvtap with disconnected physical interface

Dear list,
I just discovered the hard way that if the lower lever physical 
interface of a macvlan bridge is disconnected (ie: by unplugging the eth 
cable, resulting in no carrier), inter-guest network traffic from all 
virtual machines bound to the disconnected interface is dropped.

This behavior surprises me, as with the classic bridges I can disconnect 
the underlying physical interface without causing any harm to 
inter-guest traffic.

Am I doing something wrong, or this really is the expected behavior? If 
so, can I force the macvtap interfaces to bridge traffic even when the 
underlying physical interface is disconnected?

Regards.

-- 
Danti Gionatan
Supporto Tecnico
Assyoma S.r.l. - www.assyoma.it
email: g.danti at assyoma.it - info at assyoma.it
GPG public key ID: FF5F32A8

On Mon, May 02, 2022 at 03:42:05AM +0200, Gionatan Danti
wrote:
> Dear list,
> I just discovered the hard way that if the lower lever physical interface
of
> a macvlan bridge is disconnected (ie: by unplugging the eth cable,
resulting
> in no carrier), inter-guest network traffic from all virtual machines bound
> to the disconnected interface is dropped.
> 
> This behavior surprises me, as with the classic bridges I can disconnect
the
> underlying physical interface without causing any harm to inter-guest
> traffic.
> 
> Am I doing something wrong, or this really is the expected behavior? If so,
> can I force the macvtap interfaces to bridge traffic even when the
> underlying physical interface is disconnected?
Can you share the <interface> configuration for your guest NIC so we
can see how it is setup.

With regards,
Daniel
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