Known Issues

This page documents the list of known issues in Kubermatic KubeOne along with possible workarounds and recommendations.

This list applies to KubeOne 1.7 releases. For KubeOne 1.6, please consider the v1.6 version of this document. For earlier releases, please consult the appropriate changelog.

Cilium CNI is not working on clusters running CentOS 7

StatusKnown Issue
GitHub issueN/A


Cilium CNI is not supported on CentOS 7 because it’s using too older kernel version which is not supported by Cilium itself. For more details, consider the official Cilium documentation.


Please consider using an operating system with a newer kernel version, such as Ubuntu, Rocky Linux, and Flatcar. See the official Cilium documentation for a list of operating systems and versions supported by Cilium.

Internal Kubernetes endpoints unreachable on vSphere with Cilium/Canal

StatusWorkaround available
GitHub issue



  • Unable to perform CRUD operations on resources governed by webhooks (e.g. ValidatingWebhookConfiguration, MutatingWebhookConfiguration, etc.). The following error is observed:
Internal error occurred: failed calling webhook "webhook-name": failed to call webhook: Post "https://webhook-service-name.namespace.svc:443/webhook-endpoint": context deadline exceeded
  • Unable to reach internal Kubernetes endpoints from pods/nodes.
  • ICMP is working but TCP/UDP is not.


On recent enough VMware hardware compatibility version (i.e >= 15 or maybe >= 14), CNI connectivity breaks because of hardware segmentation offload. cilium-health status has ICMP connectivity working, but not TCP connectivity. cilium-health status may also fail completely.


sudo ethtool -K ens192 tx-udp_tnl-segmentation off
sudo ethtool -K ens192 tx-udp_tnl-csum-segmentation off

These flags are related to the hardware segmentation offload done by the vSphere driver VMXNET3. We have observed this issue for both Cilium and Canal CNI running on Ubuntu 22.04.

We have two options to configure these flags for KubeOne installations: