Elastic Network Interfaces (ENI) in AWS: The Key to Flexible Networking

Amazon Web Services (AWS) offers a wide range of networking tools to give users control over how their applications interact within a Virtual Private Cloud (VPC). One such critical component is the Elastic Network Interface (ENI), a versatile and flexible virtual network card that you can attach to your EC2 instances. In this article, we will dive into what ENIs are, how they work, and why they are essential for building resilient, scalable, and highly available cloud architectures.

What is an Elastic Network Interface (ENI)?

An Elastic Network Interface (ENI) is a logical component in a VPC that represents a virtual network card. Just like a physical network interface in a traditional server, an ENI provides a network interface that you can attach to an EC2 instance for communication within a VPC and the wider internet. ENIs are incredibly flexible and can be created independently of instances, allowing for dynamic configurations and high availability setups.

Each ENI can have the following attributes:

• A primary private IPv4 address.
• One or more secondary private IPv4 addresses.
• One Elastic IP (EIP) per private IPv4 address.