title: mongodb replica sets and ec2 - what is the host name
body: <p>I have two instances of ec2 and I want to create replica sets.  My question for the host..is it the dns name?  e.g. </p>
  
  <pre><code>rs.add("ec2-50-xx-xxx-xxx.compute-1.amazonaws.com")
  </code></pre>
  
  <p>If not...then what is?</p>
  
  <p>Thanks</p>