Chapter 2. Migrating from OpenShift SDN network plugin to OVN-Kubernetes network plugin

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"
       }
     }

     Note

     OVN-Kubernetes reserves the following IP address ranges:

     100.64.0.0/16. OVN-Kubernetes uses this IP address range for the internalJoinSubnet parameter by default.

     100.88.0.0/16. OVN-Kubernetes uses this IP address range for the internalTransSwitchSubnet parameter by default.

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

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

   $ ocm post /api/clusters_mgmt/v1/clusters/{cluster_id}/migrations
     --body=myjsonfile.json

   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"
   }

   where:

   {cluster_id}

   Specifies the ID of the cluster you want to migrate to the OVN-Kubernetes network plugin.

   myjsonfile.json

   Specifies the name of the JSON file you created in the previous step.