<p>I am planning to setup a kubernetes cluster, that looks as follows: 
<a href="https://i.stack.imgur.com/ELhad.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/ELhad.png" alt="enter image description here"></a></p>

<p>As you can see on the image, the cluster will consist of 3 Ubuntu 18.04 Virtual Private Server, one is the master and the other two servers are nodes. 
For the kubernetes installation, I am going to choose <a href="https://kubespray.io/#/" rel="nofollow noreferrer">kubespray</a>. 
First, I have to care about, that the 3 VPS can communicate with each other. That is the first question, what do I have to do, that the 3 VPS server can
communicate to each other?  </p>

<p>The second question is, how and where do I have to install kubespray? I would guess on the master server.</p>

softshipper
<p>I would start with understanding how the setup of Kubernetes cluster for your use case looks like.
There is a useful <a href="https://hostadvice.com/how-to/how-to-set-up-kubernetes-in-ubuntu/" rel="nofollow noreferrer">guide</a> about this. Showing the dependencies, installing components, deploying a pod network step by step.</p>
<p>Answering your first question:
When you initialize your master with <code>kubeadm init</code> you can join your nodes to it (<code>kubeadm join</code>).
After that you need to install and configure a pod network. <a href="https://github.com/coreos/flannel#flannel" rel="nofollow noreferrer">Flannel</a> is one of the most used network plugins for Kubernetes.</p>
<p>For your second question:
There is a <a href="https://kubernetes.io/docs/setup/production-environment/tools/kubespray/" rel="nofollow noreferrer">guide</a> from the official Kubernetes documentation about this. Prerequisites should be met on all the servers in order to make Kubespray work. <a href="https://github.com/kubernetes-sigs/kubespray" rel="nofollow noreferrer">Here</a> is the official GitHub link. However the installation steps there are minimal os I suggest supplementing with <a href="https://dzone.com/articles/kubespray-10-simple-steps-for-installing-a-product" rel="nofollow noreferrer">this</a> and <a href="https://medium.com/@sarangrana/getting-started-with-kubernetes-part-3-kubespray-on-premise-installation-guide-90194f08be4e" rel="nofollow noreferrer">this</a>.</p>
