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Migrating from OpenShift SDN network plugin to OVN-Kubernetes network plugin

As an OpenShift Dedicated cluster administrator, you can initiate the migration from the OpenShift SDN network plugin to the OVN-Kubernetes network plugin and verify the migration status using the OCM CLI.

Some considerations before starting migration initiation are:

  • The cluster version must be 4.16.24 and above.

  • The migration process cannot be interrupted.

  • Migrating back to the SDN network plugin is not possible.

  • Cluster nodes will be rebooted during migration.

  • There will be no impact to workloads that are resilient to node disruptions.

  • Migration time can vary between several minutes and hours, depending on the cluster size and workload configurations.

Initiate migration using the OpenShift Cluster Manager API command-line interface (ocm) CLI

You can only initiate migration on clusters that are version 4.16.24 and above.
Prerequisites

OpenShift Cluster Manager API command-line interface (ocm) is a Technology Preview feature only. For more information about the support scope of Red Hat Technology Preview features, see Technology Preview Features Support Scope.
Procedure

  1. Create a JSON file with the following content:

    {
  "type": "sdnToOvn"
}

    • Optional: Within the JSON file, you can configure internal subnets using any or all of the options join, masquerade, and transit, along with a single CIDR per option, as shown in the following example:

      {
  "type": "sdnToOvn",
  "sdn_to_ovn": {
    "transit_ipv4": "192.168.255.0/24",
    "join_ipv4": "192.168.255.0/24",
    "masquerade_ipv4": "192.168.255.0/24"
  }
}

      OVN-Kubernetes reserves the following IP address ranges:

      100.64.0.0/16. This IP address range is used for the internalJoinSubnet parameter of OVN-Kubernetes by default.

      100.88.0.0/16. This IP address range is used for the internalTransSwitchSubnet parameter of OVN-Kubernetes by default.

      If these IP addresses have been used by OpenShift SDN or any external networks that might communicate with this cluster, you must patch them to use a different IP address range before initiating the limited live migration. For more information, see Patching OVN-Kubernetes address ranges in the Additional resources section.

  2. To initiate the migration, run the following post request in a terminal window:

    $ ocm post /api/clusters_mgmt/v1/clusters/{cluster_id}/migrations (1)
  --body=myjsonfile.json (2)
    1 Replace {cluster_id} with the ID of the cluster you want to migrate to the OVN-Kubernetes network plugin.
    2 Replace myjsonfile.json with the name of the JSON file you created in the previous step.
    Example output
    {
  "kind": "ClusterMigration",
  "href": "/api/clusters_mgmt/v1/clusters/2gnts65ra30sclb114p8qdc26g5c8o3e/migrations/2gois8j244rs0qrfu9ti2o790jssgh9i",
  "id": "7sois8j244rs0qrhu9ti2o790jssgh9i",
  "cluster_id": "2gnts65ra30sclb114p8qdc26g5c8o3e",
  "type": "sdnToOvn",
  "state": {
    "value": "scheduled",
    "description": ""
  },
  "sdn_to_ovn": {
    "transit_ipv4": "100.65.0.0/16",
    "join_ipv4": "100.66.0.0/16"
  },
  "creation_timestamp": "2025-02-05T14:56:34.878467542Z",
  "updated_timestamp": "2025-02-05T14:56:34.878467542Z"
}
Verification

  • To check the status of the migration, run the following command:

    $ ocm get cluster $cluster_id/migration (1)
    1 Replace $cluster_id with the ID of the cluster that the migration was applied to.
Additional resources

Patching OVN-Kubernetes address ranges