controlPlaneEgressMode

Specifies the control plane egress routing mode for the cluster. If the cluster is set to AWS_MANAGED, Amazon EKS manages the egress path from the control plane and you don't need to configure NAT gateways or other routing infrastructure for control plane traffic. If the cluster is set to CUSTOMER_ROUTED, you manage the egress path from the control plane in your VPC subnets. You are responsible for ensuring that the control plane can reach required endpoints such as webhook servers and OIDC providers. The default value is AWS_MANAGED. Once set to CUSTOMER_ROUTED, this setting cannot be changed back to AWS_MANAGED on the same cluster.

Amazon EKS User Guide.