Subnets and Pods

Some subnets are reserved by Kubernetes and can prevent proper cluster deployment if you unknowingly configure DKP so that the Node subnet collides with either the Pod or Service subnet.

Ensure your subnets do not overlap with your host subnet because they cannot be changed after cluster creation. If you need to change the Kubernetes subnets, you must do this at cluster creation.

The default subnets used in DKP are:

spec:
  clusterNetwork:
    pods:
      cidrBlocks:
      - 192.168.0.0/16
    services:
      cidrBlocks:
      - 10.96.0.0/12

In Konvoy, the default pod subnet is 192.168.0.0/16, and the default service subnet is 10.96.0.0/12. If you wish to change the subnets you can do so with the following steps:

1. Generate the YAML manifests for the cluster using the --dry-run and -o yaml flags, along with the desired dkp cluster create command:

   CODE

   dkp create cluster preprovisioned --cluster-name ${CLUSTER_NAME} --control-plane-endpoint-host <control plane endpoint host> --control-plane-endpoint-port <control plane endpoint port, if different than 6443> --dry-run -o yaml > cluster.yaml

2. To modify the service subnet, add or edit the spec.clusterNetwork.services.cidrBlocks field of the Cluster object:

   CODE

   kind: Cluster
   spec:
     clusterNetwork:
       services:
         cidrBlocks:
         - 10.0.0.0/12

3. To modify the pod subnet, edit the Cluster and calico-cni ConfigMap resources:

   Cluster: Add or edit thespec.clusterNetwork.pods.cidrBlocks field:

   CODE

   kind: Cluster
   spec:
     clusterNetwork:
       pods:
         cidrBlocks:
         - 172.16.0.0/16

   ConfigMap: Edit the data."custom-resources.yaml".spec.calicoNetwork.ipPools.cidr field with your desired pod subnet:

   CODE

   apiVersion: v1
   data:
     custom-resources.yaml: |
       apiVersion: operator.tigera.io/v1
       kind: Installation
       metadata:
         name: default
       spec:
         # Configures Calico networking.
         calicoNetwork:
           # Note: The ipPools section cannot be modified post-install.
           ipPools:
           - blockSize: 26
             cidr: 172.16.0.0/16
   kind: ConfigMap
   metadata:
     name: calico-cni-<cluter-name>

When you provision the cluster, the configured pod and service subnets will be applied.