Transit Gateway for Inter- and Intra-Regional Communication


VPC Fundamentals
What is a VPC?
VPC Security and Control
VPC Connectivity
VPC Sharing using the AWS Resource Access Manager
Feature Spotlight:
Start course
3h 12m

In this section of the AWS Certified Advanced Networking - Specialty learning path, we introduce you to the various networking and VPC services currently available in AWS that are relevant to the ANS-C01 exam.

Learning Objectives

  • Identify and describe the various networking services available in AWS
  • Describe how to configure an Amazon Virtual Private Cloud (VPC)
  • Understand how to control network traffic via Security Groups and Network Access Control Lists (NACLs)
  • Describe options for VPC connectivity, subnets, and routing
  • Understand how to share VPC resources using the AWS Resource Access Manager (RAM)
  • Identify how to evaluate the configuration of VPC resources using the VPC Reachability Analyzer


The AWS Certified Advanced Networking - Specialty certification has been designed for anyone with experience designing, implementing, and operating complex AWS and hybrid networking architectures. Ideally, you’ll also have some exposure to the nuances of AWS networking, particularly regarding the integration of AWS services and AWS security best practices. Many exam questions will require advanced level knowledge of many AWS services, including AWS networking services. The AWS Cloud concepts introduced in this course will be explained and reinforced from the ground up.


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
Learning Paths

Stuart has been working within the IT industry for two decades covering a huge range of topic areas and technologies, from data center and network infrastructure design, to cloud architecture and implementation.

To date, Stuart has created 150+ courses relating to Cloud reaching over 180,000 students, mostly within the AWS category and with a heavy focus on security and compliance.

Stuart is a member of the AWS Community Builders Program for his contributions towards AWS.

He is AWS certified and accredited in addition to being a published author covering topics across the AWS landscape.

In January 2016 Stuart was awarded ‘Expert of the Year Award 2015’ from Experts Exchange for his knowledge share within cloud services to the community.

Stuart enjoys writing about cloud technologies and you will find many of his articles within our blog pages.