I manage to get VM directly on external network. A few things to describe my environment: 3 controller/network nodes in HA with external interface configured. And a few compute nodes without external interface configured.

Usually I would use floating IPs in which case the traffic from VM on a compute host would route via the v-router on the controller/network node. In this setup, trying to simply create a VM on the external network didn't work.

I had to manually configure the external interface on the compute hosts as ports (openvswitch) on br-ex. Given br-ex an ip on the external network and added default route for the external network.

After network restart could see (via ovs-vsctl show) the "phy-br-ex" interface port on br-ex which is peered with "int-br-ex". After this, VMs created directly on external network would get accessible IP on the external network.

I am not sure if this can be done any other way, for example let traffic be routed via the network nodes instead of having the compute node directly accessing the external network.

Hello,

I am not sure if it will work, however, you can try to create an external network that is shared. That will allow the network to be selected at time of VM creation as a network interface. Also, I would imagine that your compute node would need public internet connectivity.

Again, not sure if this will work, however, I am sure that you can create a shared public network which can be selected at time of VM creation.