AWS EC2 and VPC security groups

Question

According to the AWS Security White Paper

Note, however, that you must create VPC security groups specifically for your Amazon VPC; any Amazon EC2 security groups you have created will not work inside your Amazon VPC.

When I create a security group in the EC2 management console, the same gets reflected in the VPN management console. So, I was under the impression that both are the same.

I cannot find any other references in the AWS documentation mentioning that there are two types of security groups and the differences between them. Can anyone provide more information on the same?

Answer 1

If you created your AWS account in the last 3 years, you need not worry about it since EC2 classic is not offered anymore. Before AWS introduced VPC, there was EC2 classic. Security groups have to be identified with a VPC or no VPC. When you create a security group, you have to specify the domain: VPC or EC2 (No VPC).

If you are planning to use the security group in one of your VPCs, choose the VPC from VPC dropdown. If your service offers EC2 Classic, you will see No VPC in the dropdown.

Differences Between EC2-Classic and EC2-VPC