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As I have seen very large deployments still on nova networks 

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> Il giorno 07/mag/2015, alle ore 12:56, BYEONG-GI KIM <kimbyeonggi at gmail.com> ha scritto:
> 
> Dear Joe
> 
> Thank you very much for the reply!
> 
> The answer is very helpful for me to understand what multi-host mode of nova-network exactly provides. By the way, in aspect of reliability, robustness and fault-tolerance for networking service on OpenStack, nova-network still seems better than neutron, the neutron provides lots of useful networking features though. I'd like to hear comments about this. 
> 
> I'm now mainly focusing on analyzing how much high-availability can be guaranteed by each networking service type. I know the latest neutron provides distributed L3 service, i.e., DVR (Distributed Virtual Router) and can give high-availability via Pacemaker or something like that, but I'm not sure this can be said that the neutron is obviously better than nova-network in terms of the service continuity. 
> 
> Regards
> 
> Byeong-Gi
> 
> 2015-05-08 0:56 GMT+09:00 Joe Topjian <joe at topjian.net>:
>> 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 It seems that this question would be quite outdated question, because this is a question about nova-network instead of neutron.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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