Transit Gateway for Inter- and Intra-Regional Communication
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In this course, we discuss how our services deployed to AWS communicate with each other. We cover what communication looks like when our services are in the same region and what communication looks like when our services are in different regions.

Learning Objectives

  • Inter-regional communication patterns
  • Intra-regional communication patterns

Intended Audience

  • Anyone working with AWS Networking 
  • Those studying for the AWS Networking Specialty certification
  • Anyone studying for the AWS Solutions Architect certifications
  • Anyone just looking to increase their AWS knowledge


  • Before attending this course, you should already be familiar with AWS networking services such as VPCs and VPC peering



In this lesson, we will discuss using transit gateways for inter and intra-regional communication. Transit gateway is an alternative to VPC peering. Instead of each VPC peering with other VPCs, each VPC attaches to a transit gateway. Transit gateway acts as a hub in a hub and spoke design. As well as allowing multiple VPCs to route to each other, transit gateways also allow attached VPCs to share a site-to-site VPN connection or a Direct Connect connection, as well as sharing a single route to the Internet. 

Transit gateways are a regional service. VPCs in the EU West 2 must be attached to a transit gateway in EU West 2. To connect VPCs in different regions, you can create a transit gateway in each region and then peer the two transit gateways. By peering the two transit gateways, the VPCs in each region will be able to reach to each other. Using transit gateway to connect your VPCs offers benefits and drawbacks when compared to VPC peering.

Benefits of using transit gateway instead of VPC peering include shared connections to on-premises and the Internet, increased scalability. When using VPC peering, you can have 50 active VPC peers per VPC. When you use a transit gateway, you can have to 5,000 attachments per gateway. When working with transit gateway, we can use multiple route tables to control the flow of traffic through the transit gateway. Each attachment is associated with one route table. Using multiple route tables means that we can control which VPC can route to each other. Transit gateway supports equal cost multi-path routing (ECMP). ECMP allows you to use active-active connectivity to your on-premises networks, allowing you to make full use of all the bandwidth available to you.

Transit gateway offers support for software-defined wide area network connectivity using a feature called AWS Transit Gateway Connect and the GRE protocol to simplify connectivity between your offices. Drawbacks of using transit gateway instead of VPC peering include: Cost; transit gateway is more expensive than VPC peering. When using transit gateway, you are charged per hour for each attachment to your transit gateway and a price per gigabyte of data processed. Like VPC peering, data found between VPCs attached to a transit gateway stays on the AWS backbone.


About the Author

Mike has worked in IT since 1997, specializing in networking, storage, and architecture. He's been in cloud computing for the last 8 years, working across several cloud platforms but specializing in AWS. He's been involved in many cloud projects over the years covering migrations, hybrid connectivity, security optimization, networking, and storage architecture.

He gained his first training qualification in 1998 and, about 3 years ago, became an AWS Authorized Champion Instructor. He's delivered AWS cloud courses across Europe for a range of clients, with a focus on Architecture, Security, and Networking. He currently holds certifications for the four biggest cloud vendors, including the AWS Solutions Architect Professional, AWS DevOps Engineer, and AWS Advanced Networking specialty certifications.

He lives in the North of England with his wife Frances and their dog Inca.