Tags: Preview

Testing out the Azure Firewall Preview

Azure Firewall was released for preview this week, so I thought I would give it a quick try and look at some of the features available. The firewall provides the following features at the current time:

  • Built-in high availability – built into the Azure Platform, so no requirement to create load balanced configurations
  • Unrestricted cloud scalability – the firewall can scale to meet your requirements and meet changing traffic demands
  • FQDN filtering – outbound HTTP/S traffic can be filtered on a specific set of domain names without requiring SSL termination
  • Network traffic filtering rules – centrally create allow or deny network filtering rules, based on IP, port, and protocol. Azure Firewall is fully stateful, and rules can be enforced and logged across multiple subscriptions and VNETs.
  • Outbound SNAT support – outbound virtual network traffic IP addresses are translated to the Azure Firewall Public IP so you can identify and allow VNET traffic to remote Internet Destinations
  • Azure Monitor logging –  All Firewall events are integrated with Azure Monitor. This allows archiving of logs to a storage account, streaming to Event Hub, or sending them to Log Analytics.

You can read more about the features here: https://docs.microsoft.com/en-us/azure/firewall/overview

Getting access to the Azure Firewall is easy – it’s built directly into the VNET Configuration window:

However, before we can use this, we need to enable the Public Preview for our Subscription with a few PowerShell commands:

Register-AzureRmProviderFeature -FeatureName AllowRegionalGatewayManagerForSecureGateway -ProviderNamespace Microsoft.Network
Register-AzureRmProviderFeature -FeatureName AllowAzureFirewall -ProviderNamespace Microsoft.Network

You’ll need to wait upto 30 minutes at this point for the request to be enabled – see https://docs.microsoft.com/en-us/azure/firewall/public-preview for further information. You can run the following commands to check the status:

Get-AzureRmProviderFeature -FeatureName AllowRegionalGatewayManagerForSecureGateway -ProviderNamespace Microsoft.Network
Get-AzureRmProviderFeature -FeatureName AllowAzureFirewall -ProviderNamespace Microsoft.Network

If all is well – it should look like this:

Finally, run the following command to complete the setup:

Register-AzureRmResourceProvider -ProviderNamespace Microsoft.Network

Before we can add a Firewall to a VNET, we need to create a subnet called “AzureFirewallSubnet” – this is to allow the firewall to communicate with addresses on the VNET. Once this is completed, we can setup the Firewall. This is just a case of filling in some basic details:

Once we have completed the basic details, we can review and complete the deployment:

Now that the Firewall is created, we are ready to start testing. In order to test the Firewall out, we need a subnet that is routed out via this Firewall. To do this, I used a route table that directs traffic to the Firewall IP:

We now have a Subnet within our VNET that is routed via the Azure Firewall – so now we can test out some rules. My lab environment is now setup as below (Note the jump VM in a separate Subnet that is NOT routed to the Firewall. This is to allow me to RDP to the test box as I have no VPN in place to test from etc.):

From the Test VM, internet access is now blocked – because there is no firewall rule in place to allow it. I am going to add an “Application Rule collection” which I will use to allow HTTPS access to jakewalsh.co.uk, but not HTTP access. This is configured from the Firewall management interface via the Azure Portal:

Then you will be presented with the following window:

Once I have clicked on “Add” the rule will be added to the Azure Firewall. From my test VM, access to https://jakewalsh.co.uk works, but note that HTTP does not:



The same also works in reverse, so we can selectively block HTTP or HTTPS sites as we require.

As well as the Application Rules we can deploy, we can also create more traditional firewall rules (replace

Overall, the Azure Firewall complements and extends the functionality of Network security groups and gives additional control over networks residing within Azure. The rules are simple to adjust and easy to work with. It will be promising to see how this feature develops over the coming months…