What is ENI?
An elastic network interface is a logical networking component in a VPC that represents a virtual network card. You can create and configure network interfaces and attach them to instances that yhou launch in the same Availability Zone. The attributes of a network interface follow it as it’s attached or detached from an instancce and reattached to another instance. When you move a network interface from one instance to another, network traffic is redirected from the original instance to the new instance.
Note that this AWS resource is referred to as a network interface in the AWS Management Console and the Amazon EC2 API. Therefore, we use “network interface” in this documentation instead of “elastic network interface”. Then term “network interface” in this documentation always means “elastic network interface”.