How to – Migrate Azure Firewall from Classic Rules to Policy

If you have been using Azure Firewall since it went GA, you are most likely using the classic option. This means all rules are managed within the Azure Firewall resource itself. As a result, you’ve most likely noticed the below context menu pop up when accessing your resource:

The fact there is a portal driven option I personally think is great. Often “classic to new” scenarios require a rebuild, or several shell based commands. However, I found the docs a bit light in terms of details.

So this post will provide a bit more context. On the portal, you are presented with two options, migrate the existing rules to a new policy, or, attach an existing policy. Meaning you could build your policy from scratch and simply attach it, with the operation then removing the classic rules entirely.

My preference here is to attach an existing policy, however, I am not going to start from scratch. As part of creating a new firewall policy, on the rule tab, you can import your Azure Firewall rules.

This means you can capture your existing configuration, work on any changes in advance, then simply attach your newly updated policy

Two more clicks, and the Azure Firewall will replace the classic rules config with your policy. And this is the really important part – without any downtime. However, ensure you remember with my choice, I am building the policy in advance, if I make changes to that policy, they will be adhered to once live. So your changes may cause impact, but the operation of switching to policy will not.

That’s it, you’re done! A change such as this to Azure Firewall can be a concern, especially if it is handling all of your environment traffic. But this process is simple and straight forward.

As always, if any questions get in touch! Oh and if you would prefer to do this via Powershell, here are the details.

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