AKS Cluster API Server FQDN not registered with Azure DNS

Question

I recently deployed an AKS Cluster using terraform but I cannot connect to it using the API Server FQDN visible from the portal as it doesn't appear to have registered itself with Azure DNS.

I googled for solutions and found the following troubleshooting guide, but although it mentions checking the DNS of the FQDN for the API Server, it doesn't mention how to correct the problem if the FQDN does not resolve. https://learn.microsoft.com/en-us/troubleshoot/azure/azure-kubernetes/connectivity/troubleshoot-cluster-connection-issues-api-server

I've tried "reconciling" the cluster using "az aks update" but this doesn't appear to have corrected the missing DNS entry. Can anyone suggest how I can fix this please and what may have caused it?

Additionally, since I can't get the FQDN to resolve, I could potentially just add a static entry into my local hosts file for now, but could anyone tell me how I can identify the private IP of the API server without the FQDN please?

Thanks,

James

Answer 1

Hello James McGuire,

Thanks for posting your question in the Microsoft Q&A forum.

The FQDN resolution failure typically stems from missing links between the Private DNS Zone and your custom DNS infrastructure:

• Link the Private DNS Zone to your VNet: AKS automatically creates a Private DNS Zone during deployment. This zone must be linked to the VNet hosting your custom DNS servers.
• Verify Conditional Forwarding: Ensure your custom DNS server forwards requests for privatelink.<region>.azmk8s.io to Azure’s built-in DNS. Conditional forwarding rules must cover subdomains.

For DNS servers in a separate VNet or subscription: Navigate to the Private DNS Zone in the AKS-managed resource group. Under Virtual network links, add a link to the VNet where your DNS servers reside

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