We are retiring EC2-Classic. We recommend that you migrate from EC2-Classic to a VPC. For more information, see Migrate from EC2-Classic to a VPC in the Amazon Elastic Compute Cloud User Guide.
Unlinks (detaches) a linked EC2-Classic instance from a VPC. After the instance has been unlinked, the VPC security groups are no longer associated with it. An instance is automatically unlinked from a VPC when it's stopped.