Demo Service Types

In this guide, you’ll learn about the four primary Kubernetes Service types—ClusterIP, NodePort, Headless, and ExternalName—using a sample NGINX deployment. Understanding these service types will help you expose applications both inside and outside your cluster.

Overview of Service Types

Before diving in, we’ve deployed three NGINX pods with the label role=nginx in the default namespace:

kubectl get pods
# OUTPUT
# NAME                                  READY   STATUS    RESTARTS   AGE
# nginx-deployment-7ff69d756-8qdv8      1/1     Running   0          3m
# nginx-deployment-7ff69d756-hccjn      1/1     Running   0          3m
# nginx-deployment-7ff69d756-stpmz      1/1     Running   0          3m

1. ClusterIP (Default)

ClusterIP is the Kubernetes default service type. It allocates a virtual IP reachable only within the cluster.

1.1 Service Definition

apiVersion: v1
kind: Service
metadata:
  name: clusterip-svc
  namespace: default
spec:
  type: ClusterIP
  selector:
    role: nginx
  ports:
    - name: http
      port: 80
      targetPort: 80

kubectl apply -f clusterip-svc.yaml
kubectl get svc clusterip-svc
# OUTPUT
# NAME             TYPE        CLUSTER-IP       EXTERNAL-IP   PORT(S)   AGE
# clusterip-svc    ClusterIP   10.102.157.139   <none>        80/TCP    5m

1.2 Testing Internal Access

Launch a temporary pod to test DNS and HTTP:

kubectl run -i --tty --rm debug --image=curlimages/curl --restart=Never -- sh

Inside the debug pod:

nslookup clusterip-svc.default.svc.cluster.local
curl http://clusterip-svc.default.svc.cluster.local
# Should return the NGINX welcome page

2. NodePort

NodePort exposes a Service on each Node’s IP at a static port, allowing external traffic.

2.1 Service Definition

apiVersion: v1
kind: Service
metadata:
  name: nodeport-svc
  namespace: default
spec:
  type: NodePort
  selector:
    role: nginx
  ports:
    - name: http
      port: 80
      targetPort: 80
      nodePort: 30000

kubectl apply -f nodeport-svc.yaml
kubectl get svc nodeport-svc
# OUTPUT
# NAME             TYPE        CLUSTER-IP       EXTERNAL-IP   PORT(S)         AGE
# nodeport-svc     NodePort    10.98.229.84     <none>        80:30000/TCP    5m

2.2 Access via Node IP

1. Find a node’s IP address:

   kubectl get node node01 -o jsonpath='{.status.addresses[?(@.type=="InternalIP")].address}'
   # e.g., 192.168.121.156
   

2. From outside the cluster:

   curl http://192.168.121.156:30000
   

   This should return the NGINX welcome page.

2.3 Internal DNS Resolution

Within the cluster, you can still resolve the service by DNS:

kubectl run -i --tty --rm debug --image=curlimages/curl --restart=Never -- sh
# Inside the pod:
nslookup nodeport-svc.default.svc.cluster.local
curl http://nodeport-svc.default.svc.cluster.local

3. Headless Service

A headless Service omits the cluster IP (clusterIP: None) and returns the IPs of individual pods directly.

3.1 Service Definition

apiVersion: v1
kind: Service
metadata:
  name: headless-svc
  namespace: default
spec:
  clusterIP: None
  selector:
    role: nginx
  ports:
    - name: http
      port: 80
      targetPort: 80

kubectl apply -f headless-svc.yaml
kubectl get svc headless-svc
# OUTPUT
# NAME            TYPE        CLUSTER-IP   EXTERNAL-IP   PORT(S)   AGE
# headless-svc    ClusterIP   None         <none>        80/TCP    5m

3.2 DNS and Direct Pod Access

kubectl run -i --tty --rm debug --image=curlimages/curl --restart=Never -- sh

Inside the debug pod:

nslookup headless-svc.default.svc.cluster.local
for ip in $(nslookup headless-svc.default.svc.cluster.local | grep Address | awk '{print $2}'); do
  curl http://$ip
done

4. ExternalName

ExternalName maps a Service to an external DNS name by returning a CNAME record.

4.1 Service Definition

apiVersion: v1
kind: Service
metadata:
  name: externalname-svc
  namespace: default
spec:
  type: ExternalName
  externalName: httpbin.org

kubectl apply -f externalname-svc.yaml
kubectl get svc externalname-svc
# OUTPUT
# NAME                 TYPE           CLUSTER-IP   EXTERNAL-IP   PORT(S)   AGE
# externalname-svc     ExternalName   <none>       <none>        <none>    5m

4.2 Testing ExternalName

kubectl run -i --tty --rm debug --image=curlimages/curl --restart=Never -- sh
# Inside the pod:
curl http://externalname-svc.default.svc.cluster.local/get
# This request is forwarded to httpbin.org/get

Further Reading & References

• Kubernetes Services
• Service Types
• DNS for Services and Pods