Table Of Contents
What Is A Nat Gateway?  How Do NAT Gateways Work? How Does NAT Gateway Pricing Work? Why Is NAT Gateway So Expensive? How To Reduce NAT Gateway Costs Catch, Control, And Optimize NAT Gateway Costs With CloudZero

We are often asked about areas where customers overspend on Amazon Web Services (AWS). NAT gateway costs are high due to misplaced data transfers and are definitely near the top of our list.

This article will walk you through five steps you can take to find out which data transfers you’re overspending on and how you can eliminate those excess charges.

Table Of Contents

What Is A Nat Gateway? 

A Network Address Translation (NAT) gateway is an AWS-managed, highly-available service that enables you to connect instances within a private subnet of an Amazon Virtual Private Cloud (VPC) to the internet.

This is because private subnets do not have a way to connect with the internet (path to an internet gateway). 

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How Do NAT Gateways Work?

NAT gateways allow your private network to communicate with the internet or other public networks. You can use them to send and receive traffic from a single IP address without revealing your hosts’ identities. NAT gateways help secure instances within your private network by blocking all ingress traffic and allowing egress traffic. 

A great use case for this is when you’re ready to push out software updates across your organization but don’t want to give software update servers from the internet direct access to devices on your private network.

Here’s a quick look at how a NAT gateway works inside the AWS public cloud

how-nat-gateways-workCredit: AWS

You can still specify whether to create a public or private connectivity type in AWS.  

Before the NAT gateway, you needed to enable NAT for instances in a private subnet.

What is the difference between NAT gateway and NAT instances in AWS?

A NAT instance is an EC2 instance that performs functions similar to a NAT gateway. A NAT instance differs from a NAT gateway in that the latter is an AWS-managed service while NAT instances are self-managed. 

You do all the route configuration, rightsizing, and operating system and software updates when you own a NAT instance. A NAT instance is like using an Amazon EC2 instance rather than Amazon RDS to host a database. A NAT instance is ideal for advanced users who need this level of customization.

What is the difference between NAT gateway and internet gateway?

An internet gateway is a highly available, redundant, and horizontally scalable VPC component that enables communication between the internet and a VPC. Even if a Virtual Private Cloud had an IP address, none of its components would access the internet without an internet gateway. 

Unlike a NAT gateway that has a per hour per gigabyte charge, an internet gateway does not attract charges. A NAT gateway connects the private subnet to the internet through the public subnet first and the internet gateway afterward. In contrast, an internet gateway directly connects the entire VPC to the internet. 

This is how it looks visually:

NAT Gateway Traffic DiagramCredit: U-Turn Data

Still, while VPC owners create a NAT gateway within the public subnet, an internet gateway is like a router that sits at the edge of the network. Speaking of NAT charges, how much do NAT gateway data transfers cost in AWS?

How Does NAT Gateway Pricing Work?

AWS charges you per hour that a provisioned NAT gateway is available to you and per gigabyte of data transmitted through the provisioned NAT gateway. Think of that as a NAT gateway-hour and data processing charges for each gigabyte of data you transfer through the provisioned NAT gateway, regardless of the data’s origin or destination. 

Also, AWS NAT gateway prices are region-specific and factor in availability zones, so the final price you receive will vary. 

NAT Gateway Pricing

Also, AWS charges each partial hour used as a full hour consumed. There are also additional fees for standard data transfers through NAT gateways. 

However, there are often cheaper alternatives depending on where you’re sending that data (inside of AWS or outside), your region, availability zone, and your security requirements.

Picture this. NAT gateway is like living in an apartment building with a doorman. People from the outside can mail you packages to your building’s address without knowing which apartment you live in. Your doorman will then route that package to your apartment. 

However, every time you send or receive packages, you pay the doorman a fee. If you’re sending the package within your apartment community (Amazon), there are cheaper ways to do it.

Why Is NAT Gateway So Expensive?

Transmitting data with a NAT gateway can be expensive because there are multiple fees involved; hourly charge for using NAT gateway, data processing charge for NAT gateway, standard EC2 data transfer charge, and even more fees if you send data outside the Amazon ecosystem (the internet) through a NAT gateway. 

Add all these factors together, and your NAT gateway costs can add up:

NAT Gateway Tweet

Credit: Corey Quinn on Twitter with tips to reduce AWS NAT gateway costs  

In addition, some organizations forget that a NAT gateway is unnecessary to transfer data. Instead, you could set up and use a Type VPC endpoint gateway to avoid hourly and data processing fees when sending data to or from Amazon S3.

To reduce NAT gateway costs, you need to know what kind of data is being transferred and where it’s going. You can then start to replace some of them with cheaper options. We suggest starting with:

How To Reduce NAT Gateway Costs

1. Determine what types of data transfers occur the most

Reduce Your NAT Gateway Costs - Step 1

The best place to start is by figuring out which kinds of data transfers occur most in your organization. After this, you can have a better idea of how to reduce NAT Gateway costs stemming from your company’s primary traffic source.

VPC Flow Logs hold details about your NAT gateway traffic, so you want to ensure that they are enabled. You can find instructions for that here. Next, navigate to the CloudWatch console and select Insights from the navigation panel. Click on the dropdown to choose the log group linked to your NAT gateway.

Run the following script to determine which instances pass the most data through your NAT gateway. Note: x.x.x.x represents your NAT gateways private IP Address, while y.y. represents the first and second octets of the VPC CIDR range.

filter (dstAddr like 'x.x.x.x' and srcAddr like 'y.y.') 

| stats sum(bytes) as bytesTransferred by srcAddr, dstAddr

| sort bytesTransferred desc

| limit 10

Run the following script to see what data your instances are sending to- or receiving from the internet.

filter (dstAddr like 'x.x.x.x' and srcAddr like 'y.y.')

or (srcAddr like 'xxx.xx.xx.xx' and dstAddr like 'y.y.')

| stats sum(bytes) as bytesTransferred by srcAddr, dstAddr

| sort bytesTransferred desc

| limit 10

Run the following script to see from which destinations your instances upload data to the most.

filter (srcAddr like 'x.x.x.x' and dstAddr not like 'y.y.') 

| stats sum(bytes) as bytesTransferred by srcAddr, dstAddr

| sort bytesTransferred desc

| limit 10

Run the following script to see from which destinations your instances download data from the most.

filter (dstAddr like 'x.x.x.x' and srcAddr not like 'y.y.')

| stats sum(bytes) as bytesTransferred by srcAddr, dstAddr

| sort bytesTransferred desc

| limit 10

Once you’ve figured out where you’re transferring a lot of data, you’ll also want to figure out which AWS services they are using. In particular, you should know which ones are using Amazon S3 and AWS DynamoDB. This may require a little digging, but will be helpful for the next steps.

2. Eliminate costly cross availability zone transfer charges

Reduce Your NAT Gateway Costs - Step 2

The next step to reduce NAT Gateway costs is to confirm that these high-traffic instances are within the NAT Gateway’s Availability Zone. If your instances are in a different availability zone from your NAT Gateway, you don’t have to delete your instances. Instead, create new NAT Gateways in the same availability zone as your instances.


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3. Consider sending Amazon S3 and Dynamo traffic through gateway VPC endpoints instead of NAT Gateways

Reduce Your NAT Gateway Costs - Step 3

AWS offers free and low cost alternatives to NAT Gateway if you’re sending data within AWS. On example of that is VPC Endpoints. VPC Endpoints are a free alternative to NAT Gateway, but can only talk to S3 or DynamoDB.

If you’ve discovered that your NAT Gateway cost is comprised of data transfers to those two services within the same region, you can use these instructions to establish a Gateway VPC endpoint.

4. Consider setting up interface VPC endpoints instead of NAT Gateways for other Intra-AWS traffic

Reduce Your NAT Gateway Costs - Step 4

If you’re sending traffic to an AWS service that is not S3 or Dynamo DB, you can still use a lower cost alternative: Interface VPC endpoints. For a cost-savings estimate according to the number of VPC endpoints per availability zones, gigabytes of data processed, and your instances’ (or any other services’) regions, see here.

5. Depending on security requirements, consider replacing Your NAT Gateway with an internet gateway

Reduce Your NAT Gateway Costs - Step 5

For data transfers that are going to resources outside of AWS, you could potentially use an Internet Gateway. Like VPC endpoints, internet gateways are a no-cost alternative to NAT Gateways, but there are tradeoffs to consider.

One concern is that in order to use internet gateways, your instances must be in public subnets.

However, internet gateways have the added benefit of providing Internet Access Management (IAM) for added security through the use of security groups and network access control lists. This approach can mitigate some risk. If you have a security team, you can talk to them about the best way to structure this.

Catch, Control, And Optimize NAT Gateway Costs With CloudZero

The cost of data transfer through NAT gateways is one of the four horsemen of the big data apocalypse. Storage, shaping, and access to your data are the others.   

Now picture this:

Confusing NAT Gateway Costs

In this image, you can see the many ways you could rack up data transfer costs in AWS. Some extremely complex rules govern data movement, which makes it difficult for companies to account for its costs.

That the data is highly variable and unpredictable does not make it any easier to link it to processes, products, or people that produce it. This makes it difficult to predict data transfer costs, for example.

With CloudZero, you can collect, analyze, and link data transfer costs, such as NAT gateway transfer costs, to the cost centers that generated them. This can not only help you forecast and allocate costs more accurately in AWS.

It can also empower you to determine which data transfer methods you can pause, change, or delete to lower costs without sacrificing data security during transmission.

With CloudZero’s cost anomaly detection, you are also notified immediately your AWS costs approach your set threshold, so you can avoid going over budget. Want to see how CloudZero can save you money on data transfers? Schedule a demo today!    

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