May 25, 2024


This put up was co-authored by Suren Jamiyanaa, Product Supervisor II, Azure Networking.

As giant organizations throughout all industries broaden their cloud enterprise and operations, one core standards for his or her cloud infrastructure is to make connections over the web at scale. Nonetheless, a typical outbound connectivity problem encountered when dealing with large-scale outbound visitors is supply community tackle translation (SNAT) port exhaustion. Every time a brand new connection to the identical vacation spot endpoint is revamped the web, a brand new SNAT port is used. SNAT port exhaustion happens when all out there SNAT ports run out. Environments that usually require making many connections to the identical vacation spot, similar to accessing a database hosted in a service supplier’s information heart, are vulnerable to SNAT port exhaustion. In terms of connecting outbound to the web, clients have to not solely contemplate potential dangers similar to SNAT port exhaustion but additionally easy methods to present safety for his or her outbound visitors.

Azure Firewall is an clever safety service that protects cloud infrastructures towards new and rising assaults by filtering community visitors. All outbound web visitors utilizing Azure Firewall is inspected, secured, and undergoes SNAT to hide the unique consumer IP tackle. To bolster outbound connectivity, Azure Firewall might be scaled out by associating a number of public IPs to Azure Firewall. Some large-scale environments could require manually associating as much as tons of of public IPs to Firewall in an effort to meet the demand of large-scale workloads, which generally is a problem to handle long-term. Accomplice locations additionally generally have a restrict on the variety of IPs that may be whitelisted at their vacation spot websites, which might create challenges when Firewall outbound connectivity must be scaled out with many public IPs. With out scaling this outbound connectivity, clients are extra vulnerable to outbound connectivity failures on account of SNAT port exhaustion.

That is the place community tackle translation (NAT) gateway is available in. NAT gateway might be simply deployed to an Azure Firewall subnet to robotically scale connections and filter visitors via the firewall earlier than connecting to the web. NAT gateway not solely gives a bigger SNAT port stock with fewer public IPs however NAT gateway’s distinctive technique of SNAT port allocation is particularly designed to deal with dynamic and large-scale workloads. NAT gateway’s dynamic allocation and randomized number of SNAT ports considerably cut back the danger of SNAT port exhaustion whereas additionally maintaining overhead administration of public IPs at a minimal.

On this weblog, we’ll discover the advantages of utilizing NAT Gateway with Azure Firewall in addition to easy methods to combine each into your structure to make sure you have the most effective setup for assembly your safety and scalability wants for outbound connectivity.

Advantages of utilizing NAT Gateway with Azure Firewall

One of many best advantages of integrating NAT gateway into your Firewall structure is the scalability that it gives for outbound connectivity. SNAT ports are a key part to creating new connections over the web and distinguishing totally different connections from each other coming from the identical supply endpoint. NAT gateway gives 64,512 SNAT ports per public IP and might scale out to make use of 16 public IP addresses. This implies, when totally scaled out with 16 public IP addresses, NAT gateway gives over 1 million SNAT ports. Azure Firewall, however, helps 2,496 SNAT ports per public IP per digital machine occasion inside a digital machine scale set (minimal of two cases). Which means to realize the identical quantity of SNAT port stock as NAT gateway when totally scaled out, Firewall could require as much as 200 public IPs. Not solely does NAT gateway provide extra SNAT ports with fewer public IPs, however these SNAT ports are allotted on demand to any digital machine in a subnet. On-demand SNAT port allocation is essential to how NAT gateway considerably reduces the danger of widespread outbound connectivity points like SNAT port exhaustion.

NAT gateway additionally gives 50 Gbps of knowledge throughput for outbound visitors that can be utilized consistent with a typical SKU Azure Firewall, which gives 30 Gbps of knowledge throughput. Premium SKU Azure Firewall gives 100 Gbps of knowledge throughput.

With NAT gateway you additionally be sure that your outbound visitors is completely safe since no inbound visitors can get via NAT gateway. All inbound visitors is topic to safety guidelines enabled on the Azure Firewall earlier than it may possibly attain any personal sources inside your cloud infrastructure.

To be taught extra concerning the different advantages that NAT gateway presents in Azure Firewall architectures, see NAT gateway integration with Azure Firewall.

Find out how to get probably the most out of utilizing NAT Gateway with Azure Firewall

Let’s check out easy methods to arrange NAT gateway with Azure Firewall and the way connectivity to and from the web works upon integrating each into your cloud structure.

Manufacturing-ready outbound connectivity with NAT Gateway and Azure Firewall

For manufacturing workloads, Azure recommends separating Azure Firewall and manufacturing workloads right into a hub and spoke topology. Introducing NAT gateway into this setup is easy and might be accomplished in only a couple quick steps. First, deploy Azure Firewall to an Azure Firewall Subnet throughout the hub digital community (VNet). Connect NAT gateway to the Azure Firewall Subnet and add as much as 16 public IP addresses and also you’re accomplished. As soon as configured, NAT gateway turns into the default route for all outbound visitors from the Azure Firewall Subnet. Which means internet-directed visitors (visitors with the prefix routed from the spoke Vnets to the Hub Vnet’s Azure Firewall Subnet will robotically use the NAT gateway to attach outbound. As a result of NAT gateway is totally managed by Azure, NAT gateway allocates SNAT ports and scales to satisfy your outbound connectivity wants robotically. No further configurations are required.


Figure shows a diagram of a hub and spoke network setup where the spoke virtual network that contains three virtual machines is peered to the hub virtual network. Azure Firewall and NAT gateway are attached to the Azure Firewall Subnet in the hub virtual network. The diagram shows how traffic from the virtual machines in the spoke virtual network connect outbound to the internet through NAT gateway. Return and inbound traffic is sent through Azure Firewall before reaching the virtual machines in the spoke virtual network.

Determine: Separate the Azure Firewall from the manufacturing workloads in a hub and spoke topology and connect NAT gateway to the Azure Firewall Subnet within the hub digital community. As soon as configured, all outbound visitors out of your spoke digital networks is directed via NAT gateway and all return visitors is directed again to the Azure Firewall Public IP to take care of stream symmetry. 

Find out how to arrange NAT Gateway with Azure Firewall

To make sure that you’ve arrange your workloads to path to the Azure Firewall Subnet and use NAT gateway for connecting outbound, observe these steps:

  1. Deploy your Firewall to an Azure Firewall Subnet inside its personal digital community. This would be the Hub Vnet.
  2. Add NAT gateway to the Azure Firewall Subnet and connect at the very least one public IP tackle.
  3. Deploy your workloads to subnets in separate digital networks. These digital networks would be the spokes. Create as many spoke Vnets to your workload as wanted.
  4. Arrange Vnet peering between the hub and spoke Vnets.
  5. Insert a path to the spoke subnets to route web visitors to the Azure Firewall.
  6. Add a community rule to the Firewall coverage to permit visitors from the spoke Vnets to the web.

Discuss with this tutorial for step-by step steering on easy methods to deploy NAT gateway and Azure Firewall in a hub and spoke topology.

As soon as NAT gateway is deployed to the Azure Firewall Subnet, all outbound visitors is directed via the NAT gateway. Usually, NAT gateway additionally receives any return visitors. Nonetheless, within the presence of Azure Firewall, NAT gateway is used for outbound visitors solely. All inbound and return visitors is directed via the Azure Firewall in an effort to guarantee visitors stream symmetry.


  1. Can NAT gateway be utilized in a safe hub digital community structure with Azure Firewall?
    1. No, NAT gateway is just not supported in a safe hub (vWAN) structure. A hub digital community structure as described above should be used as an alternative.
  2. How does NAT gateway work with a zone-redundant Azure Firewall?
    1. NAT gateway is a zonal useful resource that may present outbound connectivity from a single zone for a digital community no matter whether or not it used with a zonal or zone-redundant Azure Firewall. To be taught extra about easy methods to optimize your availability zone deployments with NAT gateway, seek advice from our final weblog.

Advantages of NAT Gateway with Azure Firewall

In terms of offering outbound connectivity to the web from cloud architectures utilizing Azure Firewall, look no additional than NAT gateway. The advantages of utilizing NAT gateway with Azure Firewall embody:

  1. Easy configuration. Connect NAT gateway to the Azure Firewall Subnet in a matter of minutes and begin connecting outbound instantly. No further configurations required.
  2. Totally managed by Azure. NAT gateway is totally managed by Azure and robotically scales to satisfy the demand of your workload.
  3. Requires fewer static public IPs. NAT gateway might be related to as much as 16 static public IP addresses which permits for simple whitelisting at vacation spot endpoints and easier administration of downstream IP filtering guidelines.
  4. Supplies a better quantity of SNAT ports for connecting outbound. NAT gateway can scale to over 1 million SNAT ports when configured to 16 public IP addresses.
  5. Dynamic SNAT port allocation ensures that the total stock of SNAT ports is offered to each digital machine in your workload. This in flip helps to considerably cut back the danger of SNAT port exhaustion that’s widespread with different SNAT strategies.
  6. Safe outbound connectivity. Ensures that no inbound visitors from the web can attain personal sources inside your Azure community. All inbound and response visitors is topic to safety guidelines on the Azure Firewall.
  7. Greater information throughput. A regular SKU NAT gateway gives 50 Gbps of knowledge throughput. A regular SKU Azure Firewall gives 30 Gbps of knowledge throughput.

Be taught extra

For extra data on NAT Gateway, Azure Firewall, and easy methods to combine each into your architectural setup, see:


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