Documentation for changing cluster MTU has missing information about OpenshiftSDN CNI. It is complete for OVN-Kubernetes, however important information and steps for OpenshiftSDN are missing. Only Docs for 4.14 are correct.

The overhead information for the OpenshiftSDN is missing. We need to add that for SDN cluster network MTU must be 50 less.

https://docs.openshift.com/container-platform/4.16/networking/changing-cluster-network-mtu.html#mtu-value-selection_changing-cluster-network-mtu
https://docs.openshift.com/container-platform/4.16/networking/changing-cluster-network-mtu.html#mtu-value-selection_changing-cluster-network-mtu:~:text=complete%20the%20procedure.-,Prerequisites,-You%20have%20installed

  Then in the final step to finalize MTU change the command to path the OpenshiftSDN config is missing. We should have something like this:

 $ oc patch Network.operator.openshift.io cluster --type=merge --patch '{"spec": { "migration": null, "defaultNetwork":{ "openshiftSDNConfig": { "mtu": <mtu> }}}}'

https://docs.openshift.com/container-platform/4.15/networking/changing-cluster-network-mtu.html
https://docs.openshift.com/container-platform/4.16/networking/changing-cluster-network-mtu.html   

  OCP  4.15 and 4.16

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