title: How to give a VPC and all its instances access to a AWS Security Group
body: <p>My goal is simple:</p>
  
  <p>Allow any instance inside a VPC to connect to a specific security group.</p>
  
  <p>The field for allowed sources suggests: "CIDR, IP or Security group".</p>
  
  <p>Is there a way for me to specify a VPC?</p>
  
  <p>The reason beeing that I have multiple instances inside a VPC with different security groups but all need access to the security group I am creating.</p>