On OpenShift 4.16; provision 4 vlan interfaces with the following configs in (reproducer) steps below. 
- Observe that virtual machines are provisioned properly and vms come online successfully with the target networks
- Observe after a day or so, vms are offline and vlan interfaces can no longer reach the gateway.
- Rebuilding the interfaces and configs will grant another day or so of connectivity - unclear what is killing the interfaces but is blocking go-live for major project.    

    4.16.10

    twice now - customer env

    1. Deploy the following template config for creating a net-attach-definition and nncp:    

 apiVersion: nmstate.io/v1
kind: NodeNetworkConfigurationPolicy
metadata:
  name: ovs-br${VLANTAG}-vlan
spec:
  nodeSelector:
node-role.kubernetes.io/worker: ''
  desiredState:
interfaces:
- name: ovs-br-${VLANTAG}
  description: |-
    A dedicated OVS bridge with eth1 as a port
    allowing all VLANs and untagged traffic
  type: ovs-bridge
  state: up
  bridge:
    allow-extra-patch-ports: true
    options:
      stp: false
    port:
    - name: bond0
ovn:
  bridge-mappings:
  - localnet: localnet-vlan${VLANTAG}
    bridge: ovs-br-${VLANTAG}
    state: present

...

apiVersion: k8s.cni.cncf.io/v1
kind: NetworkAttachmentDefinition
metadata:
  name: localnet-vlan${VLANTAG}
  namespace: ${VMPROJECT}
spec:
  config: |2
{
        "cniVersion": "0.4.0",
        "name": "localnet-vlan${VLANTAG}",
        "type": "ovn-k8s-cni-overlay",
        "topology": "localnet",
        "netAttachDefName": "${VMPROJECT}/localnet-vlan${VLANTAG}",
        "vlanID": ${VLANTAG}
}

 - Vms come online, are accessible - fail after `n` hours and are not recoverable   

    virtualized machines and sub-network interfaces should remain stable after provisioning. 
Nodes/vms/network resources were not power cycled or migrated to customer knowledge during this timeframe (weekend). 

    Observing the ovsvctl outputs on the nodes we see that vlan23 remained accessible but vlan 18, 16, 20 are unavailable:


~~~
$ less 0070-sosreport-w-7/sosreport/sos_commands/openvswitch/ovs-appctl_fdb.stats-show_ovs-br-23

Statistics for bridge "ovs-br-23":
  Current/maximum MAC entries in the table: 1168/8192
  Current static MAC entries in the table : 0
  Total number of learned MAC entries     : 377359
  Total number of expired MAC entries     : 376191
  Total number of evicted MAC entries     : 0
  Total number of port moved MAC entries  : 0

$ less 0070-sosreport-w-7/sosreport/sos_commands/openvswitch/ovs-appctl_fdb.show_ovs-br-23 | wc -l
1169


~~~

On the other hand, the br-16 has only one in the port 2. This explains why this is not communication outside:

~~~
$ cat 0070-sosreport-w-7/sosreport/sos_commands/openvswitch/ovs-appctl_fdb.show_ovs-br-16 
 port  VLAN  MAC                Age
    2    16  02:xx:xx:xx:xx:5d    0

~~~

We can see differences in the patch between br-23 and br-16:

~~~
$ less 0070-sosreport-w-7/sosreport/sos_commands/openvswitch/ovs-vsctl_-t_5_show

    Bridge ovs-br-16
        Port patch-localnet.vlan16_ovn_localnet_port-to-br-int
            Interface patch-localnet.vlan16_ovn_localnet_port-to-br-int
                type: patch
                options: {peer=patch-br-int-to-localnet.vlan16_ovn_localnet_port}
    Bridge ovs-br-23
        Port bond0
            Interface bond0
                type: system
~~~