Increase k8s cluster CIDR

Note

Calico IPPools have to be inside the cluster-cidr

Hint

The extended cluster-cidr could be 10.224.0.0/11 which contains our old cluster-cidr (10.244.0.0/16)

Steps to change the cluster-cidr:

1. Change podSubnet in kubeadm configmap: kube-system/kubeadm-config

2. Change clusterCIDR in kube-proxy configmap: kube-system/kube-proxy

3. Change cluster-cidr on every master node: /etc/kubernetes/manifests/kube-controller-manager.yaml

   kubelet will automatically recreate the kube-controller container

4. add additional calico ippools:

   apiVersion: projectcalico.org/v3
   kind: IPPool
   metadata:
     name: additional-ippool-10.224
   spec:
     blockSize: 26
     cidr: 10.224.0.0/16
     ipipMode: Always
     natOutgoing: true
     nodeSelector: all()
     vxlanMode: Never
   

   => IPPools have to be applied with calicoctl instead of kubectl.

5. Optional: change pod_subnet in /var/lib/metal-controller/{CLUSTER}/config/config.toml in the metal-controller running in the deploy cluster.

   Hint

   This is just for documentation purposes because kubeadm picks for new masternodes the range specified in the kubeadm configmap