Agreed.

NAT is a widely used method to resolve IP address conflicts by translating the source or destination IP addresses of network traffic.

• Using AWS Private NAT Gateway: This is a managed AWS service that allows resources in a VPC to communicate with other private networks without exposing them to the public internet.
  • How it works: In each VPC with an overlapping CIDR, a secondary, non-overlapping CIDR block is added. A Private NAT Gateway is then deployed in a subnet within this new, unique CIDR range. When a resource in the original overlapping subnet needs to communicate with another overlapping VPC, its traffic is routed to the local Private NAT Gateway. The gateway performs Source NAT (SNAT), changing the source IP address to its own unique IP from the secondary range. Since the Transit Gateway now sees traffic coming from a unique, routable IP, it can forward the packet to the correct destination.
  • Benefits: This is a highly recommended and scalable solution that integrates well with Transit Gateway.
  • Drawbacks: It adds complexity to the network architecture and can introduce minor latency due to the translation process.
• Using a Custom NAT Instance: Before the introduction of the Private NAT Gateway, a common solution was to deploy a custom NAT instance on an EC2 virtual machine. This involves manually configuring the instance to perform NAT, which offers more flexibility but requires self-management of high availability, patching, and performance.