问CDH的kerberos启动后,hdfs的datanode就无法找到namenode？

Caused by: java.io.IOException: Couldn't setup connection for hdfs/cdh2@DCI.COM to cdh3/172.26.60.87:8022
	at org.apache.hadoop.ipc.Client$Connection$1.run(Client.java:710)
	at java.security.AccessController.doPrivileged(Native Method)
	at javax.security.auth.Subject.doAs(Subject.java:415)
	at org.apache.hadoop.security.UserGroupInformation.doAs(UserGroupInformation.java:1917)
	at org.apache.hadoop.ipc.Client$Connection.handleSaslConnectionFailure(Client.java:681)
	at org.apache.hadoop.ipc.Client$Connection.setupIOstreams(Client.java:769)
	at org.apache.hadoop.ipc.Client$Connection.access$3000(Client.java:396)
	at org.apache.hadoop.ipc.Client.getConnection(Client.java:1557)
	at org.apache.hadoop.ipc.Client.call(Client.java:1480)
	... 10 more
	
	
	出现这样的错误