Unable to add nodes after OpenShift SDN to OVN migration if the node is built before migration

Environment

• Red Hat OpenShift Container Platform 4.x

Issue

• I am unable to add new nodes after OpenShift SDN to OVN migration if the node is built before migration

Resolution

• Ensure the nodes you add into the cluster are built after migration to allow the node to fetch the latest configurations from Machine Config Servers.

Root Cause

• The MCO will always try to boot new nodes on the latest MachineConfig. If the nodes are booted before migration, they will be unable to join the cluster due to a mismatch of networking causing the kubelet to never become ready.

Diagnostic Steps

You may see the following error in your logs. If so, try this KCS first. Otherwise, proceed with the steps in this KCS.

container runtime network not ready: NetworkReady=false reason:NetworkPluginNotReady message:Network plugin returns error: 
No CNI configuration file in /etc/kubernetes/cni/net.d/

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