title: AWS allow trafic from another Elastic beanstalk or EC2 with changing IP
body: <p>I have 2 accounts where one is a Elastic Beanstalk (Account A). I want another account(B) EC2 should allow traffic only from account A's Elastic Beanstalk.
  How to handle this if the IP of Elastic Beanstalk from account A changes.</p>