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Below you will find details on various compatibility issues and quirks that you may be effected by in your environment.


When Google configure the control plane for private clusters, they automatically configure VPC peering between your Kubernetes cluster's network and a separate Google managed project.

In order to restrict what Google are able to access within your cluster, the firewall rules configured restrict access to your Kubernetes pods. This will mean that you will experience the webhook to not work and experience errors such as Internal error occurred: failed calling admission webhook ... the server is currently unable to handle the request.

In order to use the webhook component with a GKE private cluster, you must configure an additional firewall rule to allow the GKE control plane access to your webhook pod.

You can read more information on how to add firewall rules for the GKE control plane nodes in the GKE docs.


When using a custom CNI (such as Weave or Calico) on EKS, the webhook cannot be reached by cert-manager. This happens because the control plane cannot be configured to run on a custom CNI on EKS, so the CNIs differ between control plane and worker nodes.

To address this, the webhook can be run in the host network so it can be reached by cert-manager, by setting the webhook.hostNetwork key to true on your deployment, or, if using Helm, configuring it in your values.yaml file.

Note that since kubelet uses port 10250 by default on the host network, the webhook.securePort value must be changed to a different, free port.


Disabling the webhook is not supported anymore since v0.14.