[Openstack] [neutron][nova] vif_plugging_is_fatal significance?

Kevin Benton blak111 at gmail.com
Fri Feb 6 07:39:34 UTC 2015

Nova sends a port update to Neutron after the VM has been scheduled so
Neutron can know the location of the port it needs to setup in OVS. After
Neutron finishes this setup, it notifies Nova that it has finished setting
up the port. At this point, Nova resumes the boot of the VM since network
connectivity is now supposed to be present.

vif_plugging_timeout is how long Nova will wait to hear back from Neutron
that the port is active.
vif_plugging_is_fatal determines what Nova does when that timer expires. If
it's true, it will error out as you observed. If it's false, it will assume
the port is ready and continue booting even though it has not heard from

Your intuition is right that you are bypassing the problem, which is the
missing notifications from Neutron to Nova. Have you confirmed that the
Neutron port is actually active and that you have connectivity?

If so, there is probably just a misconfiguration in neutron.conf for the
nova notification settings. Check the URL/region/tenant
info/username/password for all of the settings that start with 'nova_' in

If you don't have connectivity, it means that Neutron actually couldn't
bring the port online, in which case it was correct not to notify Nova. In
this case, you will need to examine your Neutron server logs (usually
/var/log/neutron/server.log) to get more hints about why it's failing to
bring up the port.

Kevin Benton

On Thu, Feb 5, 2015 at 10:06 PM, Akilesh K <akilesh1597 at gmail.com> wrote:

> Hi,
> I have a working openstack setup. But I have some questions on how I got
> it working.
> Initially my instances failed to launch.
> I have updated the correct values for neutron authentication in nova.conf
> and correct nova authentication in neutron.conf and notify_nova on port
> change is true but still instances failed.
> One thing I did note was that It took an awfully long time to fail and by
> the time it reported failure neutron had created a port for the instance,
> the vif driver had created a tap interface, the kvm had already started but
> still nova reported failure.
> When I set vif_plugging_is_fatal to false and vif_plugging_timeout to 10 I
> could finally have my Instances up and in about 20 seconds.
> Someone please explain the
> 1, significance of these two parameters
> 2. what had been going on in my openstack before I had them configured
> correctly
> 3. if even the configuration I had done is correct or am I just bypassing
> some bigger problem.
> Thank you,
> Ageeleshwar K
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Kevin Benton
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