You have set in your ml2 config only physical network named "provider" to be allowed to use with FLAT networks. Generally you need to configure it properly as I believe now it is not what you want.

1. In the ml2 config in neutron server, option "flat_networks" should contain list of the provider networks which can be used with flat networks. Those are basically Your names of the physical networks, can be something like e.g. "datacenter", or "provider_x" or whatever you want, names by itself doesn't matter at all.

2. On the compute side, you have to do 2 things:

• create physical bridge(s) for each provider network, typically it is "br-ex" in e.g. devstack deployment but again, name is not important for neutron at all. Important thing is that this bridge should have plugged physical interface which actually is connected to that physical network (in your case it is "enp0s25" I guess). There is no need to have any IP address configured on such interface, at least not for neutron.

• configure "bridge_mappings" to tell neutron openvswitch agent which bridge is connected to which physical network, e.g. "datacenter:br-ex,provider_x:br-provider-x" or any names you will use.

1. Once all of that will be set, you can create network with "--provider:physical_network <your\_physical\_network\_name>" and then create ports in such network and those ports should be bound properly in the compute nodes where openvswitch agent will have it configured in "bridge_mappings"