When you create a custom cluster, Rancher uses RKE (the Rancher Kubernetes Engine) to provision the Kubernetes cluster on your existing infrastructure.

If you don’t want to host your Kubernetes cluster in a hosted kubernetes provider or provision nodes through Rancher, you can use the custom cluster option to create a Kubernetes cluster in on-premise bare-metal servers, on-premise virtual machines, or in any node hosted by an infrastructure provider.

In this scenario, you’ll bring the nodes yourself, and then configure them to meet Rancher’s requirements. Then, use the Custom Nodes install option to set up your cluster.