AWS — Transit Gateway Overview

Introduction to AWS Transit Gateway — Getting started guide.

Awesome Cloud — AWS Transit Gateway

TL;DR:

AWS Transit Gateway is a fully managed service that connects VPCs and On-Premises networks through a central hub without relying on numerous point-to-point connections or Transit VPC.

AWS — Site-to-Site VPN Connections Overview

Key Points

• Transit Gateway is a Regional resource and can connect thousands of VPCs within the same AWS Region.
• You can create a Site-to-Site VPN connection as an attachment on a Transit Gateway. You can modify the target gateway of a Site-to-Site VPN connection from a virtual private gateway to a transit gateway.
• Transit gateway replace multiple Virtual private gateways of VPCs.
  i.e. TGW can attach to multiple VPCs, while VGW can attach to single VPC.
• When you attach a VPC to a transit gateway, you must specify one subnet from each Availability Zone to be used by the Transit Gateway to route traffic. Specifying one subnet from an Availability Zone enables traffic to reach resources in every subnet in that Availability Zone.
• Transit gateway can be shared with other AWS accounts using RAM.
• DNS Support — DNS resolution across the attachments. An instance in VPC…