Attaching FloatingIP break the connection!

In this overcloud configuration I have the controller nodes connected to Provisioning (NIC1) and also to the Public Network (NIC2).

I modified the controller.yaml file to add a new interface (NIC2) with ovn bridge (br-floating). When I create a flat external network on the floating network and use this as a gateway for the router, the VM can access the extern world (ping 8.8.8.8). But once I assign a Floating IP to this instance, the VM lost the connection, and I can ping neither out from the VM nor into it.

In the controller.yaml you can see what the modification.
I also insert these few lines the network-env.yaml:

parameter_defaults:
NeutronExternalNetworkBridge: "''"
NeutronBridgeMappings: datacentre:br-ex,floating:br-floating
NeutronFlatNetworks: datacentre,floating

The cmd I used to create the external network:
openstack network create public --external --provider-network-type flat --provider-physical-network floating

I guess its a configuration issue, and I hope someone could help in this.

Many thanks!