Hello Franck,

You may not have had to ever set this up, if you only had a single AZ in the past, however in Flamingo you might need to define:

neutron_ovn_availability_zones: ["your_az_name1","your_az_name2",”etc”]

in globals.yaml

And then create your networks with –availability-zone-hint arguments.

Source: https://docs.openstack.org/neutron/latest/admin/config-az.html

We experienced a similar issue when testing Caracal, where, if this setting was not configured, routers could be deployed to any availability zone, and therefore not be able to properly communicate outside of their AZ. It might be that Flamingo is more explicit, and requires this configuration where it was optional in the past.

Kind Regards,

Joel McLean Cyber Security and Product Development Manager Australia’s First Tier IV Data Centre https://www.micron21.com/

1300 769 972 03 9751 7618 0407 888 429 joel.mclean@micron21.com

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From: Franck VEDEL (UGA) <franck.vedel@univ-grenoble-alpes.fr>
Sent: Friday, 6 March 2026 12:03 AM
To: OpenStack Discuss <openstack-discuss@lists.openstack.org>
Subject: [kolla-ansible][flamingo][horizon] Network creation problem

Hello everyone,

I have a production OpenStack cluster for ESM students running Epoxy, deployed with Kolla-Ansible, and everything is working perfectly. I’m very satisfied with this setup.

To prepare for upgrades, I set up a new test cluster in parallel using Kolla-Ansible, but this time with Flamingo.

Everything seemed fine until I tried to create a network and its subnet in Horizon. The network is created, but no availability zone is associated with it. As a result, I cannot launch instances on this network.

Could this be a change in the new OpenStack installation process that I missed? Or is this a bug? This is the first time I’ve encountered this issue. Is there a parameter that needs to be added in the Horizon override file (_9999-custom-settings.py) to handle this?

Thanks in advance for any guidance.

Franck VEDEL