title: when tried to give more than one contact point for APP builder to connect to cassandra seeing ERROR
body: <p>Application developer in my team is working on a App builder to connect to cassandra, in properties file I have seen that he is using only one contact point, I have asked him to includes all seed nodes as contact points and changed replication from simplestrategy to NetworkTopologystrategy and code looks like this</p>
  
  <pre><code>cassandra.contactPoint=52.xxx.xx.xxx,52.xxx.xx.xxx,10.xxx.xx.xxx,10.xxx.xx.xxx
  cassandra.replicationFactor={ 'class' : 'NetworkTopologyStrategy', 'DC1' :'3' , 'DC2' : '3'}
  cassandra.dataCenter=DC1   
  cassandra.createKeyspace=false
  </code></pre>
  
  <p>Then we have seen the following error</p>
  
  <blockquote>
    <p>Invocation of init method failed; nested exception is
    java.lang.IllegalArgumentException:
    52.xxx.xx.123,52.xxx.xx.125,10.xxx.xx.xxx,10.xxx.xx.xxx    com.datastax.driver.core.Cluster$Builder.addContactPoint(Cluster.java:749)</p>
  </blockquote>
  
  <p>So I asked him to include seed nodes present in DC1 then we restarted and saw this error</p>
  
  <blockquote>
    <p>Session ERROR  - Error creating pool to /52.xxx.xx.125:9042   Caused
    by: java.net.ConnectException: Connection refused: /52.xxx.xx.125:9042</p>
  </blockquote>
  
  <p>I have few questions on this</p>
  
  <ol>
  <li><p>What does <code>cassandra.datacenter()</code> do? Do we need to specify contact points present in that particular DC? If so what should I add to that if I need to include my seed nodes involving both DC's?</p></li>
  <li><p>Even after specifying nodes belonging to that particular DC we got errors. Is this because of replication factor we have mentioned? Is the syntax of it correct?</p></li>
  </ol>