The Cluster Network Operator (CNO) deploys and manages the cluster network components in an OKD cluster. This includes deployment of the Container Network Interface (CNI) default network provider plug-in selected for the cluster during installation. For more information, see Cluster Network Operator in OKD.
The DNS Operator deploys and manages CoreDNS to provide a name resolution service to pods. This enables DNS-based Kubernetes Service discovery in OKD. For more information, see DNS Operator in OKD.
When you create your OKD cluster, pods and services running on the cluster are each allocated IP addresses. The IP addresses are accessible to other pods and services running nearby but are not accessible to external clients. The Ingress Operator implements the Ingress Controller API and is responsible for enabling external access to OKD cluster services. For more information, see Ingress Operator in OKD.
The External DNS Operator deploys and manages ExternalDNS to provide the name resolution for services and routes from the external DNS provider to OKD. For more information, see Understanding the External DNS Operator.