Hello @Thiago. It is possible to achieve communication across secured and unsecured clusters. A common use case for this is using DistCp for transfer of data between clusters. As mentioned in other answers, the configuration property ipc.client.fallback-to-simple-auth-allowed=true tells a secured client that it may enter a fallback unsecured mode when the unsecured server side fails to satisfy authentication. However, I recommend not setting this in core-site.xml, and instead setting it on the command line invocation specifically for the DistCp command that needs to communicate with the unsecured cluster. Setting it in core-site.xml means that all RPC connections for any application are eligible for fallback to simple authentication. This potentially expands the attack surface for man-in-the-middle attacks. Here is an example of overriding the setting on the command line while running DistCp: hadoop distcp -D ipc.client.fallback-to-simple-auth-allowed=true hdfs://nn1:8020/foo/bar hdfs://nn2:8020/bar/foo The command must be run while logged into the secured cluster, not the unsecured cluster. This is adapted from one of my prior answers: https://community.hortonworks.com/questions/294/running-distcp-between-two-cluster-one-kerberized.html
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