More detail
EC2 instances, Fargate tasks and VPC-attached Lambda functions all reach the VPC through ENIs. Security groups attach to ENIs, not to the thing itself.
ENI (Elastic Network Interface)
A virtual network card that gives something an address in a subnet.
Think of it as: A phone line installed in a particular room.
What to know for Level 0
- An ENI is a network card with a private IP in a subnet. EC2 instances, each Fargate task and VPC-attached Lambda functions get one, and security groups attach to ENIs, not to subnets.