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Troubleshoot the VMExtensionError_CniDownloadTimeout error code (41)

This article discusses how to identify and resolve the VMExtensionError_CniDownloadTimeout error (also known as error code ERR_CNI_DOWNLOAD_TIMEOUT, error number 41) that occurs when you try to create and deploy a Microsoft Azure Kubernetes Service (AKS) cluster.

Prerequisites

  • The Curl command-line tool

Symptoms

When you try to create a Linux-based AKS cluster, you receive the following error message:

Message: We are unable to serve this request due to an internal error

SubCode: VMExtensionError_CniDownloadTimeout;

Message="VM has reported a failure when processing extension 'vmssCSE'.

Error message: "Enable failed: failed to execute command: command terminated with exit status=41\n[stdout]\n{

"ExitCode": "41",

Cause

Your cluster nodes can't connect to the endpoint that's used to download the Container Network Interface (CNI) libraries. In most cases, this issue occurs because a network virtual appliance is blocking Secure Sockets Layer (SSL) communication or an SSL certificate.

Solution

Run a Curl command to verify that your nodes can download the binaries:

curl https://acs-mirror.azureedge.net/cni/azure-vnet-cni-linux-amd64-v1.0.25.tgz

curl --fail --ssl https://acs-mirror.azureedge.net/cni/azure-vnet-cni-linux-amd64-v1.0.25.tgz  --output /opt/cni/downloads/azure-vnet-cni-linux-amd64-v1.0.25.tgz

If you can't download these files, make sure that traffic is allowed to the downloading endpoint. For more information, see Azure Global required FQDN/application rules.

References

Contact us for help

If you have questions, you can ask Azure community support. You can also submit product feedback to Azure feedback community.

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