Kubernetes Service: ClusterIP

What Is ClusterIP?

ClusterIP is the default Service type in Kubernetes. It exposes a stable virtual IP that is reachable only inside the cluster.

When to Use It

ClusterIP is ideal for:

• frontend to backend communication
• API to database communication
• internal microservice traffic

Full YAML Example

apiVersion: v1
kind: Service
metadata:
  name: backend
spec:
  selector:
    app: backend
  ports:
    - port: 80
      targetPort: 8080
  type: ClusterIP

DNS Name Format

Inside the cluster, the full DNS name looks like this:

backend.default.svc.cluster.local

The short name backend often works inside the same namespace.

Inspect the Service

kubectl get svc
kubectl get endpoints backend

If the endpoints list is empty, the Service selector probably does not match any ready pods.

Why ClusterIP Is the Default

Most services in Kubernetes talk to each other internally. ClusterIP supports that use case without exposing anything publicly.

Think of ClusterIP like an internal office extension number. People inside the building can call it, but outside callers cannot.