Migrating from OpenshiftSDN to OVNKubernetes CNI

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APIs involved in this migrations are:

  • Network.operator.openshift.io

  • Network.config.openshift.io


Operators involved in this migrations are:

  • Cluster Network Operator (CNO)

  • Machine Config Operator (MCO)


Refer to pre-requisite steps here, jotted in another post. Update to latest compatible z-stream. 

With that taken care, proceed below.


1> Backup existing cluster network config:

    # oc get Network.config.openshift.io cluster -o yaml > cluster-openshiftSDN.yaml


2> Verify that OVN_SDN_MIGRATION_TIMEOUT environment variable is set and is 

equal to 0s.


3> Set the migration value to null in CNO object cluster:

        

     # oc patch Network.operator.openshift.io cluster --type='merge' --patch '{"spec":{"migration":null}}'



At this time,


CNO updates status of Network.config.openshift.io CR named cluster
accordingly.


MCO rolls out an update to systemd configuration necessary for OVNK, single machine per pool 

at a time in series. So time taken is proportionate to size of clusters and number of nodes in it.


4> Delete the openshiftSDN NNCP resource on primary network interface:


        # oc get nncp


        NAME STATUS REASON

    bondmaster0 Available SuccessfullyConfigured


        # oc delete nncp bondmaster0


5> Set Migration field to “networkType: OVNKubernetes” in CNO 

object cluster:


        # oc patch Network.operator.openshift.io cluster 

        --type='merge' 

        --patch '{

        "spec": 

        { "migration": 

        { "networkType":"OVNKubernetes"

        } } }'


At this time, CNO


  • Destroys the openshift SDN control plane pods.

  • Deploys OVNK control plane pods.

  • Updates the Multus daemon sets and config map objects to 

           reflect new CNI plugin.


6> Check the reboots of nodes have finished, post upgrade belonging to MCP pools, by running:


        # oc get mcp


     Status for Nodes in MCP group should be showing 'READY'


7> Check all cluster operators are avialable :


              # oc get co


8> Following parameters can be customized per needs:


       # oc patch Network.operator.openshift.io cluster 

                --type=merge 

        --patch 

                '{          

                    "spec":

                    { "defaultNetwork": { "ovnKubernetesConfig":  

                    { "mtu":<mtu>, 

                       "genevePort":<port>,             

                       "v4InternalSubnet":"<ipv4_subnet>",           

                      "v6InternalSubnet":"<ipv6_subnet>"            

                }}}}'


9> Disable few features from OpenshiftSDN, that mght have been used earlier and not supported

by OVNK.


# oc patch Network.operator.openshift.io cluster 

                --type='merge'                    

                --patch                           

                '{                                

                "spec":                            

                { "migration":                         

                { "networkType": "OVNKubernetes", " 

                features": {                        

                    "egressIP": false,               

                    "egressFirewall": false,         

                    "multicast": false               

                } } } }'    

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