The Issue

When deploying a vSphere with Tanzu guest cluster via the command line, I hit the following error:

kubectl apply -f cluster.yaml

Error from server (spec.settings.network.pods.cidrBlocks intersects with the network range of the external ip pools in network provider's configuration, spec.settings.network.pods.cidrBlocks intersects with the network range of the external ip pools LB in network provider's configuration): 

error when creating "cluster.yaml": admission webhook "default.validating.tanzukubernetescluster.run.tanzu.vmware.com" denied the request: spec.settings.network.pods.cidrBlocks intersects with the network range of the external ip pools in network provider's configuration, spec.settings.network.pods.cidrBlocks intersects with the network range of the external ip pools LB in network provider's configuration

The Cause

The default CIDR Block used by vSphere with Tanzu for the Pod Networking is 192.168.0.0/16 and for Services Networking is 10.96.0.0/12. Therefore if you have any over laps with this in your Workload Management setup, such as, in my case the Load Balancing configuration when integrating with NSX-T. You will end up with a failure.

This will happen if you use a deployment YAML for your cluster such as the below, there is no pod/service networking settings specified, so the default is chosen.

apiVersion: run.tanzu.vmware.com/v1alpha1
kind: TanzuKubernetesCluster
metadata:
  name: veducate-cluster
  namespace: deanl
spec:
  distribution:
    version: v1.18.15
  topology:
    controlPlane:
      class: best-effort-small
      count: 1
      storageClass: management-storage-policy-thin
    workers:
      class: best-effort-small
      count: 3
      storageClass: management-storage-policy-thin
  settings:
    network:
      cni:
        name: calico
    storage:
      defaultClass: management-storage-policy-thin

The Fix

The fix is quite a simple one if you are unable to change your egress and ingress networking CIDRs.

You can simply specify the Pod/Services Networking CIDR in your YAML Specification as per the below example.

apiVersion: run.tanzu.vmware.com/v1alpha1
kind: TanzuKubernetesCluster
metadata:
  name: veducate-cluster
  namespace: deanl
spec:
  distribution:
    version: v1.18.15
  topology:
    controlPlane:
      class: best-effort-small
      count: 1
      storageClass: management-storage-policy-thin
    workers:
      class: best-effort-small
      count: 3
      storageClass: management-storage-policy-thin
  settings:
    network:
      cni:
        name: calico
      pods:
        cidrBlocks: ["172.16.0.0/16"]
      services:
        cidrBlocks:  ["10.51.0.0/16"]
    storage:
      defaultClass: management-storage-policy-thin

Regards

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