Goal

The multus [default network feature](https://github.com/k8snetworkplumbingwg/multus-cni/blob/master/docs/configuration.md#specify-default-cluster-network-in-pod-annotations) allows the user to specify the default network for any given pod, whenever there are multiple cluster networks available within a Kubernetes cluster. This is something which is currently used by KubeVirt for KubeVirt multus networks, when the `Default` [knob](https://kubevirt.io/api-reference/main/definitions.html#_v1_multusnetwork) is enabled.

We want to be able to customize the primary UDN pod network attachment (i.e. allowing us to specify the MAC address of the primary UDN attachment), and doing so using the multus default network attachment seems to be the natural fit in the ecosystem. 

User Stories

• As a VM owner, I want to import my existing VM from another virtualization platform into OpenShift Virtualization, attaching it to a primary UDN, so I can have the managed experience I'm used to having, and use features like services, and network policies. The VM's MAC address must be the same when migrating.

Non-Requirements

• List of things not included in this epic, to alleviate any doubt raised during the grooming process.

Notes

• Any additional details or decisions made/needed