Monday, March 20, 2023

Auto create DNS records for RSV with policy including region code

 When using private endpoints at scale, the recommended setup from Microsoft is to use Azure Policy to automatically create the DNS records in the central private DNS zones when the private endpoints are created. The reason for this is that users or owners of the spokes or landing zones do not have permissions to create A records in the central private DNS zones in the Hub.

The policies specified by Microsoft work as long as a region code does not have to be specified in the private DNS zone name (which is the case for most of them, see full list here). However, for e.g. Recovery Services Vault for Azure Backup (and for AKS/Kubernetes), this is the case.

The zones are region specific, for West Europe it's: and for Sweden Central it's

The default policy only does a check on the subResource (or groupId) value which in this case is: AzureBackup. The result of having two policies (e.g. one for West Europe and one for Sweden Central) running with the same subResource value is that DNS records for the private endpoints are randomly generated in the two private DNS zones.

A fix for this is to add a conditional check in the policy on the location of the private endpoint (PE). This way it is ensured that the DNS records are created in the correct zone that matches the location of the PE.

The full policy is available on Github, see link here.

The main change can be seen below:

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