Architecture: Private NAT and Overlapping IP Ranges in AWS

Two teams, two projects, two VPCs. Neither team talked to the other about addressing, so both grabbed the obvious default: 10.0.0.0/16 . Everything worked fine in isolation. Then a business requirement lands: an application in VPC A needs to call a service in VPC B . You reach for VPC peering, and AWS rejects it. You reach for a Transit Gateway, attach both VPCs, and watch one of your routes silently vanish from the route table. The problem is not … Read More