OK, I found a solution, so I will post it here if anyone has the same issue.

after creation of new subnet, we need to set new ip address and unset old one on ovnmeta port:

openstack port set --fixed-ip subnet=<subnet_id>,ip-address=172.16.2.3 <ovnmeta_port_id> openstack port unset --fixed-ip subnet=<subnet_id>,ip-address=172.16.2.1 <ovnmeta_port_id>

Then when VM is created on compute node, metadata agent sets new IP in ovnmeta namespace. If namespace already exists, restart of ovn metadata agent updates the IP in ovnmeta namespace.

On Wed, Sep 20, 2023 at 11:35 AM Kamil Madac kamil.madac@gmail.com wrote:

Hi Rodolfo,

Thanks for the response, and sorry for the confusion which can be caused by my lack of knowledge about how ovn is implemented in openstack. I have seen following blueprint (not for OVN obviosly):

https://wiki.openstack.org/wiki/Neutron/enable-to-set-dhcp-port-attributes

and somehow thought that dhcp has an ip address assigned also in OVN.

When I checked it once more I found out that device_id of the port has prefix ovnmeta-, which means that it is not dhcp but metadata agent or proxy:

$ openstack port show -f table -c id -c fixed_ips -c device_id 4f70acdf-59e9-4252-9f0c-c71eb68baa9a

+-----------+---------------------------------------------------------------------------+ | Field | Value |

+-----------+---------------------------------------------------------------------------+ | device_id | ovnmeta-61d55c5b-adeb-440e-a029-796e783fdc02 | | fixed_ips | ip_address='172.16.0.1', subnet_id='4632d9e5-6918-415e-b752-9f828e57404c' | | id | 4f70acdf-59e9-4252-9f0c-c71eb68baa9a |

+-----------+---------------------------------------------------------------------------+

Is it possible to set another ip address of this port during creation of the subnet, or afterwards?

Thanks

On Wed, Sep 20, 2023 at 10:22 AM Rodolfo Alonso Hernandez < ralonsoh@redhat.com> wrote:

...

Hello Kamil:

I'm not sure what you are asking for, sorry. In ML2/OVN, the DHCP server is local (in the same compute node where the VM is spawned) and has no IP address. The local OVS instance will capture the DHCP requests and reply to them.

If you are asking for a VM port with a static IP address, this is something you can currently do creating a port and setting the fixed IP address [1].

Can you share the blueprint you are referring to? How do you plan to migrate VMs to a different cloud?

Regards.

[1]https://paste.opendev.org/show/bl87sEpUnZttIMxN9fyc/

On Wed, Sep 20, 2023 at 9:52 AM Kamil Madac kamil.madac@gmail.com wrote:

...

Hello OpenStack community,

I'd like to ask whether it's possible to set a static fixed IP address for a DHCP server within a subnet, especially when using the OVN driver. While I've come across a blueprint that addresses this topic, I haven't been able to find any pertinent details in the documentation.

Our primary use case is to maintain IP addresses during the migration of VMs between two OpenStack clouds.

Any guidance or suggestions would be greatly appreciated.

Thank you!

-- Kamil Madac

-- Kamil Madac https://kmadac.github.io/