Create an ENI using the AWS Management Console, AWS CLI, or AWS SDKs by specifying the VPC, subnet, and optionally assigning private IPv4 addresses, Elastic IPs, security groups, and tags.
You can create an Elastic Network Interface (ENI) using the AWS Management Console, AWS CLI, or AWS SDKs. When creating an ENI, you must specify the VPC and subnet in which it will reside. The ENI will receive a primary private IPv4 address from the subnet's IP address range. You can optionally assign secondary private IPv4 addresses, an Elastic IP address (after creation), security groups, and tags.
ENIs can be created in a VPC and are specific to a single Availability Zone (the same AZ as the subnet)
A primary private IP address is always assigned; you cannot create an ENI without one
You can attach an ENI to an EC2 instance only if the instance is in the same Availability Zone as the ENI's subnet
After creation, you can attach an Elastic IP address to the primary or secondary private IP addresses
ENIs have a default source/destination check enabled; disable it if the instance acts as a network appliance (NAT, router, firewall)