title: RabbitMQ Error: unable to connect to nodes : nodedown
body: <p>I am trying to do clustering using two Rhel instances. I am able to ping each other and even when i am trying to use command <code>empd -names</code>, i get it is up and running on 4369.When i am use the command as <code>sudo rabbitmqctl join_cluster rabbit@ip-10-23-20-36</code> i am getting the below error ensuring as well to i am stop_app first..</p>
  
  <pre><code>sudo rabbitmqctl join_cluster rabbit@ip-10-23-20-36
  </code></pre>
  
  <p>Clustering node 'rabbit@ip-10-23-20-36' with 'rabbit@ip-10-23-209-142' ...
  Error: unable to connect to nodes ['rabbit@ip-10-23-209-142']: nodedown</p>
  
  <h1>DIAGNOSTICS</h1>
  
  <p>attempted to contact: ['rabbit@ip-10-23-209-142']</p>
  
  <p>rabbit@ip-10-23-209-142:
    * unable to connect to epmd (port 4369) on ip-10-23-209-142: nxdomain (non-existing domain)</p>
  
  <p>current node details:
  - node name: 'rabbitmq-cli-80@ip-10-23-20-36'
  - home dir: /var/lib/rabbitmq
  - cookie hash: u7nRIpJ40Fd356iLbkDO6Q==</p>
  
  <p>Things I already tried: </p>
  
  <ol>
  <li>Checked the cookie name,which is same in both instances using<br>
       <code>sudo cat /var/lib/rabbitmq/.erlang.cookie</code>. </li>
  <li>Changed the epmd port as well <code>export  ERL_EMPD_PORT=4370</code> </li>
  <li><code>netstat -an |grep 4369 | grep -i listen</code> </li>
  <li>Changing the hostnames as well in GUI of plugin management.</li>
  <li><p>Changed owner and permission also using </p>
  
  <pre><code>sudo chown rabbitmq:rabbitmq /var/lib/rabbitmq/.erlang.cookie
  sudo chmod 400 /var/lib/rabbitmq/.erlang.cookie
  </code></pre></li>
  <li><p>Add port </p>
  
  <pre><code>sudo iptables -I INPUT -p tcp --dport 4369 --syn -j ACCEPT
  </code></pre></li>
  <li><p>sudo rabbitmqctl status </p>
  
  <pre><code>{listeners,[{clustering,25672,"::"},{amqp,5672,"::"}]},
  </code></pre></li>
  </ol>
  
  <p>*IP-Adresses are sample adrresses.</p>