OpenShift Container Platform MTU issues when applying custom MTU settings via the MachineConfigOperator in Red Hat OpenShift Container Platform 4.x

Solution Verified - Updated -

Issue

Configuring custom MTU may cause the MachineConfig Operator pods to be unable to reach the services IP before they can push custom MTU settings from MachineConfig

Trying to push jumbo frame MTU settings to nodes' physical interfaces with the MachineConfig Operator, but the MachineConfig Operator cannot reach the control plane API to get its configuration. Running curl from the affected nodes directly towards the API endpoints works, but it times out towards the API Service IP. Running netcat or telnet to the API Service IP does work (see Diagnostic Steps for further details).

Environment

  • Red Hat OpenShift Container Platform 4.X
  • OVNKubernetes as OpenShift SDN
  • Custom MTU required for OpenShift network traffic (such as jumbo frames)
  • User Provisioned Infrastructure (UPI) for any platform and Installer Provisioned Infrastructure (IPI) for baremetal

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