title: How to reference another EC2 instance, which may be restarted or even have another instance started?
body: <p>Consider an server <code>ec2-50-1-2-3.compute-1.amazonaws.com</code>, which is not publicly available and which does not have an elastic IP address. I cannot assign it an Elastic IP address as I don't have any more addresses to assign (used all 5 already on publicly-available servers).</p>
  
  <p>The publicly-available servers need to access a service on <code>ec2-50-1-2-3.compute-1.amazonaws.com</code>. However, if I restart that server then it may receive a different address and I'll have to update 20 websites across 5 webservers with the new address. Is there any way to refer to the <code>ec2-50-1-2-3.compute-1.amazonaws.com</code> server which will persist even if I restart that server, considering that I have no more Elastic IP addresses to assign to it?</p>