Using a NodePort in a Kubernetes Cluster on top of VirtualBox

Accessing applications deployed in a Kubernetes Cluster using VirtualBox requires a NodePort. In a cloud provider, a load balancer will be used.

Deploying a Kubernetes Cluster on top of VirtualBox requires a specific network configuration as seen in the Kubernetes Cluster using Vagrant and Ansible and First Steps After Kubernetes Installation tutorials.

LAN, NAT, HOST Only and Tunnel Kubernetes networks
Networking in a Kubernetes Cluster using VirtualBox

The tutorial shows how to deploy an application and a NodePort to publish the application outside the Kubernetes Cluster.


Deploying Applications in Kubernetes

Create an Application configuration file that defines the name of the application, labels, number of replicas, and the docker images that are needed. Save the file as nginx.yaml.

apiVersion: apps/v1
kind: Deployment
  name: nginx-deployment
      app: nginx
  replicas: 3
        app: nginx
        - name: my-echo

Apply the configuration to the Kubernetes Cluster

$ kubectl apply -f nginx.yaml 
deployment.apps/nginx-deployment created

The Docker image, in this example nginx, has to be available in the official public Docker Registry (if using a local Docker image, it first needs to be uploaded to the public registry or a private registry, see Pull an Image from a Private Registry or the section Building the Color Application in the Istio Patterns: Traffic Splitting in Kubernetes (Canary Release) tutorial).

Publish an Application Outside Kubernetes Cluster

In order to access the echo server that we just deployed from outside the cluster a NodePort needs to be created, the NodePort will allow us to access each of the Nginx echo servers (in round-robin) from outside the cluster.

In a Kubernetes cluster hosted in a cloud provider like Azure, Google or AWS a cloud-native Load Balancer will be used instead of the NodePort.

Add the following definition to nginx.yaml (the file created before)

apiVersion: v1
kind: Service
  name: nginx-service-np
    name: nginx-service-np
  type: NodePort
    - port: 8082        # Cluster IP, i.e.
      targetPort: 8080  # Application port
      nodePort: 30000   # (EXTERNAL-IP VirtualBox IPs) i.e.
      protocol: TCP
      name: http
    app: nginx

Apply the configuration to the Kubernetes Cluster

$ kubectl apply -f nginx.yaml 
deployment.apps/nginx-deployment unchanged
service/nginx-service-np created

Check to see if the NodePort hast been created

$ kubectl get services
NAME               TYPE           CLUSTER-IP     EXTERNAL-IP   PORT(S)          AGE
kubernetes         ClusterIP      <none>        443/TCP          7h55m
nginx-service-np   NodePort    <none>        8082:30000/TCP   5h43m

Access the application with curl (or with a web browser) from the development environment using one of the public Kubernetes Cluster IPs (,, and the NodePort (30000):

$ curl
Hostname: nginx-deployment-d7b95894f-2hpjk
Pod Information:
	-no pod information available-
Server values:
	server_version=nginx: 1.13.3 - lua: 10008
Request Information:
	real path=/
Request Headers:
Request Body:
	-no body in request-

Repeat the request and see that the value of hostname changes as Kubernetes is accessing the different instances of the application among the available PODS. The hostname corresponds to the NAME of the different PODS for the Nginx deployment:

$ kubectl get pods
NAME                               READY   STATUS    RESTARTS   AGE
nginx-deployment-d7b95894f-2hpjk   1/1     Running   1          5h44m
nginx-deployment-d7b95894f-49lrh   1/1     Running   1          5h44m
nginx-deployment-d7b95894f-wl497   1/1     Running   1          5h44m

Kubernetes NodePort Diagram

The diagram shows the different elements that are involved in publishing an application outside the Kubernetes cluster using a NodePort. The Kubernetes master, not shown, executes a proxy as well.

NodePort traffic in Kubernetes Cluster

Network traffic when doing curl

  1. A request to access (Node 1 Port NodePort) is received by the vboxnet router.
  2. It is routed the external IP of the Kubernetes node 1 in port 30000
  3. The request is sent to the Kubernetes Proxy
  4. The Kubernetes Proxy sends the request to the Cluster IP and port 8082 that has been assigned to the nginx-services-np (Nginx service NodePort).
  5. The Nginx service NodePort sends the request to one of the available pods for the application Nginx, it can be any of the pods located at the same Kubernetes node or in a different node (like K8N-N-2)

5 comments on “Using a NodePort in a Kubernetes Cluster on top of VirtualBox”

  1. running headless can access nginx app on local workstation, can you tell me easiest way to access from remote workstation / internet

  2. Congratulations on a wonderful piece of work.

    It saved me several hours of work and I have moved away from spending hours trying out different stuff to working on real life stuff that matters.



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Javier Ruiz Cloud and SaaS Expert

Javier Ruiz

IT Wonder Lab tutorials are based on the diverse experience of Javier Ruiz, who founded and bootstrapped a SaaS company in the energy sector. His company, later acquired by a NASDAQ traded company, managed over €2 billion per year of electricity for prominent energy producers across Europe and America. Javier has over 25 years of experience in building and managing IT companies, developing cloud infrastructure, leading cross-functional teams, and transitioning his own company from on-premises, consulting, and custom software development to a successful SaaS model that scaled globally.

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