What is the default service type in Kubernetes?

The default service type in Kubernetes is indeed ClusterIP. This service type is designed to provide a stable IP address for a set of pods, serving as the internal communication channel within the cluster. When a service is created without specifying a type, Kubernetes automatically assigns it the ClusterIP type.

ClusterIP allows other services or pods within the same cluster to communicate with the exposed application's pods through a virtual IP address. This type is limited to internal traffic and cannot be accessed from outside the cluster, making it ideal for internal applications or microservices that do not need to be exposed to external clients.

In contrast, the other service types are intended for different scenarios. NodePort enables services to be accessed externally by assigning a static port on each node, while LoadBalancer provisions a cloud-based load balancer to manage external traffic. ExternalName maps the service to an external DNS name but does not handle actual service traffic. Thus, for internal communication with no need for external access, ClusterIP is the most appropriate and commonly used default service type.