10 Transit Gateway Best Practices

A transit gateway is a network device that allows you to connect your on-premises network to the AWS cloud. It provides a central point of connectivity for your AWS resources and allows you to manage traffic routing in a single place.

In this article, we will discuss 10 best practices for using a transit gateway. By following these best practices, you can improve the performance and security of your transit gateway and make it easier to manage.

1. Use a single Transit Gateway for all your VPCs

When you use multiple Transit Gateways, you create what’s called a “split-horizon” network. This means that traffic destined for one VPC can only take the shortest path through the Transit Gateway, even if there’s a more direct route available.

This can lead to increased latency and decreased throughput because traffic has to take the longest path possible. It can also lead to increased costs because you’re paying for transit between your VPCs even though there’s a more direct connection available.

By using a single Transit Gateway for all your VPCs, you can avoid these problems and ensure that traffic is routed efficiently.

2. Attach only the required VPCs to the Transit Gateway

If you have a transit gateway with 10 VPCs attached to it and one of those VPCs gets compromised, the attacker now has access to the other 9 VPCs. This is because the transit gateway provides full connectivity between all the VPCs that are attached to it.

Therefore, it’s important to only attach the VPCs that actually need to be connected to the transit gateway. If you don’t need to connect all your VPCs, then don’t. This will help reduce the attack surface in the event that one of your VPCs does get compromised.

3. Create multiple routes tables and use route propagation

When you create a transit gateway, AWS creates a default route table. This is the table that’s used when you first attach a VPC to your transit gateway. However, once you have multiple VPCs attached, it’s no longer efficient to use a single route table.

Instead, you should create a separate route table for each VPC. That way, you can more easily control the traffic between your VPCs. You can also use route propagation to automatically add routes to your route tables. Route propagation allows you to specify which routes should be propagated to which route tables.

This is a crucial transit gateway best practice because it allows you to fine-tune your traffic flow and ensure that only the traffic you want flowing between your VPCs is actually flowing.

4. Use AWS Resource Access Manager (RAM) to share resources across accounts

When you use RAM to share a transit gateway, you can control which accounts have access to the gateway and what level of access they have. This is important because it allows you to limit the blast radius in the event that one account is compromised.

Additionally, using RAM to share resources across accounts helps to improve security posture by reducing the number of places where sensitive data is stored. By sharing resources through RAM, you can centralize the storage of sensitive data in a single account, which reduces the risk of data leakage.

Finally, using RAM to share resources can help to improve efficiency and optimize costs. When you share resources through RAM, you can avoid duplicating effort and resources across accounts. Additionally, by sharing resources through RAM, you can take advantage of economies of scale to reduce costs.

5. Enable Flow Logs on the Transit Gateway

Flow Logs capture information about the IP traffic flowing in and out of your Transit Gateway. This is valuable data that can be used to troubleshoot connectivity issues, monitor for suspicious activity, and more.

To enable Flow Logs, you’ll first need to create an IAM role that gives the Transit Gateway permission to write logs to CloudWatch. Then, you can enable Flow Logs on the Transit Gateway itself. After Flow Logs are enabled, you’ll start seeing log entries in CloudWatch.

6. Use tags to organize your Transit Gateways, attachments, and route tables

When you have a lot of Transit Gateways, attachments, and route tables, it can be difficult to keep track of them all. This is where tags come in handy. By tagging your resources, you can easily organize and identify them.

For example, you could tag all of your Transit Gateways with the name of the AWS account they’re associated with. Then, when you need to find a particular Transit Gateway, you can easily filter the results by account name.

Tagging your resources also makes it easier to automate Transit Gateway management tasks using scripts or AWS Lambda functions. For example, you could write a script that automatically deletes Transit Gateways that are no longer needed.

Finally, tags can help you save money on your AWS bill. Many AWS services offer discounts for customers who use tags to organize their resources.

7. Use an AWS CloudFormation template to automate the creation of the Transit Gateway

When you use an AWS CloudFormation template, you can easily version control your Transit Gateway configuration. This is important because it allows you to track changes to the Transit Gateway over time, and makes it easy to roll back to a previous version if necessary.

Additionally, using an AWS CloudFormation template ensures that your Transit Gateway is created in a consistent and repeatable manner. This is important for both troubleshooting and scaling purposes.

Finally, using an AWS CloudFormation template allows you to share your Transit Gateway configuration with others, which can be helpful for collaboration purposes.

8. To create redundancy in case of a failure, attach the same VPC to multiple Transit Gateways

If you only have one Transit Gateway attached to a VPC, and that Transit Gateway fails, your VPC will lose its connection to the other VPCs it was peered with. However, if you have multiple Transit Gateways attached to the same VPC, the VPC will still be able to communicate with the other VPCs even if one of the Transit Gateways fails.

This transit gateway best practice is especially important for mission-critical applications that cannot afford to lose their connection to other VPCs.

9. If you have many VPCs, consider using a combination of transit gateways and VPN connections

If you have a lot of VPCs, it can be expensive to connect them all to a transit gateway. In this case, it might make more sense to use a combination of transit gateways and VPN connections. That way, you can connect the most important VPCs to the transit gateway for maximum performance, and then use VPN connections for the rest.

This approach can also help improve security, since VPN connections are generally more secure than transit gateway connections.

10. Monitor your network traffic with Amazon CloudWatch metrics and alarms

As your network traffic grows, it becomes more difficult to troubleshoot issues that may arise. By monitoring your transit gateway with Amazon CloudWatch, you can set alarms to notify you of potential problems so you can investigate and resolve them before they cause major disruptions.

Additionally, Amazon CloudWatch metrics can help you identify trends in your network usage over time. This information can be used to capacity plan and ensure that your transit gateway has the resources it needs to handle future growth.