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List of IPs used by each Azure Resource (service)

It is not uncommon to configure the firewall and other security and control mechanism like User Defined Routes (UDR) and NGA (Network Security Groups) to restrict access to your Azure Resources. In the moment when we want to do such a thing we need to know the IPs that are used by Azure Infrastructure.

Let’s take as example a web application that is hosted inside App Service (using VNETs, Traffic Manager, Azure Storage, Azure SQL and many more). To be able to properly configure the access rules, we need to know what are the IPs used by Azure Storage and Azure SQL in that region, Traffic Manager IPs used for probing and so on.

Azure Region IP Range
Most of this information can be found in a XML provided by Microsoft (https://www.microsoft.com/en-us/download/details.aspx?id=41653), but I expect that this will not enought. You’ll find inside the document the IP ranges that are used by each Azure Region, but without a tag that specify what IP ranges are used by each Azure Resource it is to generic. This might not be acceptable.

Granularity 
Our clients will not allow us to accept traffic from any IP that it is used by Azure in that specific region. We need a more granular approach and allow incoming/outgoing traffic only to the IP ranges used by services that we are using.
The next step that you will do would be to search inside Azure documentation to get the IP ranges for each Azure Service that you are using. For a part of the services, you might find a clear IP range. A good example is Traffic Manager that published the IPs that are used for probing (https://docs.microsoft.com/en-us/azure/active-directory/role-based-access-control-what-is).
Unfortunately, for other Azure Services this information is not available and you will need to use domain names to control access. This might not be all the time acceptable from client site and you will need to mitigate it.

IP Change Notifications
Let us assume that you manage to get the IP ranges of all Azure Resources that are involved in your system. Even if it is not per instance, but per Azure Resource type for each Azure Region is already good. Next thing that you want to do is to ensure that when the IP ranges are changed you can update the configuration.
Of course this can be a manual step for Maintenance and Support team that is done every month, week or day, but why not to do automate it. In theory this should be an easy step using Azure Automation as long as we would have a central location with all IPs used by each Azure Resource.
Unfortunately, this is not available yet and we need to find a workaround.

Workaround
The first thing that we need to do is to identify all locations where the list of IPs is published. Once you done this, you need to be ready to parse the page content and extract the IPs. This is not complicated and it shall be done easy.
Now, there are two ways on how you can monitor all this location. The simplest one is to check at a specific time interval if something was changed. A runbook would be trigger in the case of any changes.

Another approach is to register to page updates. This can be done easily using GitHub. Keep in mind that each page from Azure documentation is kept in GitHub. Nothings stop us to register to file changes to that specific page or project.

Conclusion
Try to be creative and find ways how you can collect data that we need. In this case I think that the most complex task is to find the pages where the list of IP range is publish and not to implement the solution itself.

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