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Hello,

If the nova-network service is down, then only actions that would involve
nova-network (creating and terminating instances for example) won't work.
Instances that are already running will still be able to communicate with
both the outside network and other instances in the cloud.

You can easily test this by just stopping the nova-network service on the
compute node (assuming you have a window where no one will be launching
instances).

multi-host provides continuity in that each compute node becomes a network
gateway for the instances hosted on that node. If that compute node is
physically down, instances on all other compute nodes can still have
external network access.

Contrast this with single-host networking where all traffic is routed
through the single host. (Again, nova-network does not need to be running
on that single host for traffic to still get out.)  But if that single host
is physically down, then *no* instances in your cloud have external network
access.

Hope that helps,
Joe

On Thu, May 7, 2015 at 1:08 AM, BYEONG-GI KIM <kimbyeonggi at gmail.com> wrote:

> Hello.
>
> It seems that this question would be quite outdated question, because this
> is a question about nova-network instead of neutron.
>
> I wonder whether VMs located in a Compute Node, e.g., Compute A, are
> accessible while its nova-network service is down if the other nova-network
> is running on the other Compute Nodes, such as Compute B, Compute C, etc.
>
> Or, does the multi-host just provide continuity of the networking service
> via avoiding single point failure?
>
> Thanks in advance!
>
> Regards,
> Byeong-gi
>
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