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Configuring hybrid networking

As a cluster administrator, you can configure the Red Hat OpenShift Networking OVN-Kubernetes network plugin to allow Linux and Windows nodes to host Linux and Windows workloads, respectively.

Configuring hybrid networking with OVN-Kubernetes

You can configure your cluster to use hybrid networking with the OVN-Kubernetes network plugin. This allows a hybrid cluster that supports different node networking configurations.

This configuration is necessary to run both Linux and Windows nodes in the same cluster.
Prerequisites

  • Install the OpenShift CLI (oc).

  • Log in to the cluster as a user with cluster-admin privileges.

  • Ensure that the cluster uses the OVN-Kubernetes network plugin.

Procedure

  1. To configure the OVN-Kubernetes hybrid network overlay, enter the following command:

    $ oc patch networks.operator.openshift.io cluster --type=merge \
  -p '{
    "spec":{
      "defaultNetwork":{
        "ovnKubernetesConfig":{
          "hybridOverlayConfig":{
            "hybridClusterNetwork":[
              {
                "cidr": "<cidr>",
                "hostPrefix": <prefix>
              }
            ],
            "hybridOverlayVXLANPort": <overlay_port>
          }
        }
      }
    }
  }'

    where:

    cidr

    Specify the CIDR configuration used for nodes on the additional overlay network. This CIDR must not overlap with the cluster network CIDR.

    hostPrefix

    Specifies the subnet prefix length to assign to each individual node. For example, if hostPrefix is set to 23, then each node is assigned a /23 subnet out of the given cidr, which allows for 510 (2^(32 - 23) - 2) pod IP addresses. If you are required to provide access to nodes from an external network, configure load balancers and routers to manage the traffic.

    hybridOverlayVXLANPort

    Specify a custom VXLAN port for the additional overlay network. This is required for running Windows nodes in a cluster installed on vSphere, and must not be configured for any other cloud provider. The custom port can be any open port excluding the default 4789 port. For more information on this requirement, see the Microsoft documentation on Pod-to-pod connectivity between hosts is broken.

    Windows Server Long-Term Servicing Channel (LTSC): Windows Server 2019 is not supported on clusters with a custom hybridOverlayVXLANPort value because this Windows server version does not support selecting a custom VXLAN port.
    Example output
    network.operator.openshift.io/cluster patched

  2. To confirm that the configuration is active, enter the following command. It can take several minutes for the update to apply.

    $ oc get network.operator.openshift.io -o jsonpath="{.items[0].spec.defaultNetwork.ovnKubernetesConfig}"

Additional resources