We are excited to announce ClassicLink support for Virtual Private Cloud (VPC) peering connections. This feature enables communication between linked EC2-Classic instances and resources in a peered VPC over private IP address space. The EC2-Classic instance and the peered VPC can be in different accounts. ClassicLink support for VPC peering simplifies communication between an EC2-Classic instance and a peered VPC.
For more information see ‘Configurations with ClassicLink’. You can learn more approximately ClassicLink, here.
Source: amazon.com