Get Started with Elastic Load Balancing

EC2-Classic — Instances launched in EC2-Classic run in a flat network that you share with other customers. We assign each instance with a private IP address from a range of private IP addresses for the EC2-Classic network. We also assign a public IP address for your instance. For more information about Amazon EC2, see What is Amazon EC2? in the Amazon Elastic Compute Cloud User Guide.

EC2-VPC — Instances launched in EC2-VPC run in an virtual private cloud (VPC) that is logically isolated in your AWS account. We assign each instance with a private IP address from the private IP address range of your VPC. You have complete control over the VPC assigned to you. For more information about Amazon VPC, see What is Amazon VPC in the Amazon Virtual Private Cloud User Guide.

If your AWS account comes with a default virtual private cloud (default VPC), your instances are launched within the default VPC, by default, unless you specify a subnet from a nondefault VPC. A default VPC combines the benefits of the advanced features provided by EC2-VPC with the ease of use of EC2-Classic. Your default VPC automatically comes with a default subnet in each Availability Zone, an Internet gateway connected to your default VPC, and a default security group associated with your default VPC, among other default configurations. For more information on default VPCs and subnets, see Your Default VPC and Subnets.