private void startMulticast(Attributes atts) {
    DistributedSystemConfig config = (DistributedSystemConfig) stack.peek();

    String port = atts.getValue(PORT);
    config.setMcastPort(parseInt(port));

    String address = atts.getValue(ADDRESS);
    if (address != null) {
      config.setMcastAddress(address);
    }
  }
When a <code>multicast</code> is first encountered, get the
<code>DistributedSystemConfig</code> off of the top of the stack and set its multicast config
appropriately.
geode-core/src/main/java/org/apache/geode/admin/internal/ManagedEntityConfigXmlParser.java