Some non-commercial AWS regions do not support full 9001 MTU, but hypershift and the network operator assume that 9001 should be used on hosted cluster nodes in AWS. There is currently no way to override this value for HostedCluster. It can be mitigated via activities on the worker nodes (Day 2) via migrations, but this is not desirable nor maintainable for automating large numbers of clusters.

Customers require a way to override the hardcoded MTU of 9001 during hosted cluster deployments in non-commercial AWS regions.  

References to the hardcoded MTU in the cluster network operator for hosted clusters in AWS can be found at:

https://github.com/openshift/cluster-network-operator/blob/9d540eb7929f83879d3dafbcd1ae6cb1feca36b3/pkg/controller/operconfig/mtu_probe.go#L27
https://github.com/openshift/cluster-network-operator/blob/9d540eb7929f83879d3dafbcd1ae6cb1feca36b3/pkg/controller/operconfig/mtu_probe.go#L38-L42

OpenShift 4.20 on Management Cluster;  OpenShift 4.18 on Hosted Clusters
Multicluster engine 2.10