Hi Stackers,  

Over the past few days, we encountered an issue during the migration of VMs from a customer environment to our OpenStack cloud. Both environments were connected via a cross-connect network (a VLAN-type network spanning the cloud and the customer environment), which resulted in duplicate MAC addresses in our OVN database. This occurred because the migrated VM retained the same MAC address as previously used in the customer's environment(so "ovn-sbctl list fdb" returned a port which was no-longer used and leads to such duplication) .  

To address the issue, we used the following command to clear the FDB database:  
ovn-sbctl --all destroy fdb  

While researching further, we came across the `fdb_age_threshold` configuration [1], which seemed to be a useful feature to prevent similar issues in the future. We attempted to implement it in our Kolla-Ansible environment by adding the following configuration to `/etc/kolla/config/neutron/ml2_conf.ini`:  
[ovn]  
fdb_age_threshold = 920  

After deploying the changes, however, we noticed that the setting did not take effect in OVN. The configuration only applied successfully after we executed a manual script to propagate the setting directly to OVN [2]. Anyway such change is applicable only for exsisting networks, so it is far from perfect solution.

Could you provide guidance on whether this behavior is due to incorrect documentation, an error in our configuration process, or an additional requirement needed to enable this feature? Any insights would be greatly appreciated.  

Thank you in advance for your support!