Overlay IP is a special case of networking in AWS, which is of critical importance in SAP environments that require High Availability setup. In this article, we will understand why Overlay IP is needed, technical details on how this works, and design patterns in SAP that utilize it.  

What Is Overlay IP 

In AWS networking, the private IP address within a VPC binds itself to a network interface of an EC2 instance for providing network connectivity. As the binding happens in a static manner and the instance lies within a zone, this creates a challenge for the high availability scenarios that are set up across zones. In such scenarios, the client applications will expect a single IP address for application connectivity; however, the same cannot be achieved with a static IP address.