Red Hat OpenShift Container Platform

Using an OVN-Kubernetes localnet topology to map VLANs to a secondary interface

You can use OVN-Kubernetes localnet topology in a NetworkAttachmentDefinition (NAD) to map a specific VLAN ID from the physical network to the secondary interface of a pod.

To provide multiple VLANs for cluster workloads in Red Hat OpenShift Container Platform, define additional VLANs in the NetworkAttachmentDefinition custom resource (CR). Configuring trunk ports ensures that the physical network associates correctly with your virtual infrastructure for reliable traffic management.

The example in the procedure demonstrates the following configurations:

Physical switch ports connect to Red Hat OpenShift Container Platform nodes by using VLAN trunking. The trunk carries tagged traffic for the VLANs you define in NADs.
The br-ex acts as the OVS bridge that connects virtual workloads to the physical workloads.
Multiple NADs with specific VLAN tags get created by using the localnet topology. This configuration defines specific VLAN IDs for traffic isolation.
Pods or virtual machines (VMs) attach to the NAD CRs for the purposes of improved network connectivity.

Prerequisites

You installed the OpenShift CLI (oc).
You logged in as a user with cluster-admin privileges.
You installed the NMState Operator.
You configured the br-ex bridge interface during cluster installation.

Procedure

Create an NetworkAttachmentDefinition CR for each VLAN, such as nad-cvlan100.yaml. OVN-Kubernetes uses the NAD files to tag and untag Ethernet frames for pods or VMs.

Example configuration

apiVersion: k8s.cni.cncf.io/v1
kind: NetworkAttachmentDefinition
metadata:
  name: vlan-100
  namespace: default
spec:
  config: |-
    {
      "cniVersion": "0.4.0",
      "name": "localnet-vlan-100",
      "type": "ovn-k8s-cni-overlay",
      "physicalNetworkName": "physnet",
      "topology": "localnet",
      "vlanID": 100,
      "mtu": 1500,
      "netAttachDefName": "default/vlan-100"
    }
# ...

Attach pods or VMs to the VLANs by referencing the NAD in the configuration for the pod or VM:

Example pod configuration

apiVersion: v1
kind: Pod
metadata:
  annotations:
    k8s.v1.cni.cncf.io/networks: vlan-100
# ...

Example VM configuration

apiVersion: kubevirt.io/v1
kind: VirtualMachine
spec:
    template:
        spec:
        networks:
        - multus:
            networkName: vlan-100
            name: secondary-vlan
# ...