title: AWS Security group
body: <p>I have 2 security groups A1 and A2. There are some Ec2 instances belonging to A1 or A2 ( not both ) . 
  Question - 
  Only The ec2 instances belonging to A1 should be able to access instances belonging to A2.
  i.e If I try to logon from my desktop machine ( which is not on aws ) I should not be able to connect in anyway to machine on group A2. </p>
  
  <p>Is it possible to create such a rule in aws security group ( for A2 ) as an inbound rule ?</p>
  
  <p>Thanks</p>