Why does the cost keep going up for my firewall and how do I get it to be at a fixed rate?

Question

I noticed that the cost for our firewall keeps going up everyday even though we have not any of the storage. The rate goes up by approximately $100 every day and I would like to stop it from going up too much. A few cents a day would be fine but it makes it really hard to be in the budget when it creases largely at a day rate. I would greatly appreciate your advice and suggestions.

Answer 1

Azure Firewall costs are primarily driven by two components: the fixed hourly deployment charge and variable data-processing charges based on the amount of traffic processed in gigabytes (GB). A sudden daily increase of approximately $100 typically indicates a significant rise in network throughput, increased diagnostic log ingestion into Log Analytics, or changes that caused the firewall to scale out or process additional traffic.

To identify the cost driver, review Azure Cost Analysis and separate the charges associated with the firewall deployment fee, data processing volume, and Log Analytics ingestion. Firewall metrics and structured logs should also be examined for unusual traffic patterns, such as unexpected outbound activity from compromised resources, network routing loops, excessive retries, or overly verbose diagnostic logging that is increasing ingestion volume.

To reduce costs, optimize firewall logging by reviewing which logs are required and routing them appropriately. Using resource-specific Log Analytics tables or the Basic Logs plan can reduce ingestion costs for applicable data. For development and test environments, consider deallocating the firewall outside of required usage periods through PowerShell or automation runbooks, since the hourly deployment cost continues while the firewall is provisioned. Review network and application rules for misconfigurations that may be causing unnecessary traffic flows, repeated connection attempts, or large data transfers through the firewall.

The description of the Azure Firewall pricing model and available SKUs is available at https://azure.microsoft.com/en-us/pricing/details/azure-firewall/

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hth

Marcin