That's depending on your use-case. We have two types of VMs in our 
cloud, production VMs and the rest (self-service tenant networks). All 
production VMs are in provider networks, launched with config-drive 
and independent of the control plane. So as long as the compute nodes 
and the network infrastructure are running we can work, the less 
important VMs are not reachable during that time, of course, but it 
doesn't really hurt anybody.
So if you have machines that are required to work independent of 
network nodes (control nodes) you should consider using such provider 
networks. Or move the VMs to those networks if you already have been 
using provider networks.

Zitat von Nguyễn Hữu Khôi <nguyenhuukhoinw@gmail.com>:

> Yes. I agree with you but when all controller is down and some users need
> to reboot their instances then it won't have ip. This is my worry.
>
> Nguyen Huu Khoi
>
>
> On Fri, Aug 11, 2023 at 5:00 AM Clark Boylan <cboylan@sapwetik.org> wrote:
>
>> On Thu, Aug 10, 2023, at 12:00 AM, Nguyễn Hữu Khôi wrote:
>> > Hello guys.
>> >
>> > Sometimes I see that my instances won't get IP from Neutron DHCP Agent.
>> >
>> > Is it good if we set a fixed port for instance and set a static ip in
>> > the instance's netplan configuration also?
>>
>> We do this for IPv6 addresses on some of our servers as we've had problems
>> with RAs. It seems to work fine in that case. Ideally, this shouldn't be
>> necessary for any cloud instance though and it might be worth digging into
>> why dhcp isn't working so that it can be corrected.
>>
>> >
>> >
>> > Nguyen Huu Khoi
>>