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Posted to common-commits@hadoop.apache.org by Apache Wiki <wi...@apache.org> on 2011/06/27 14:03:55 UTC

[Hadoop Wiki] Update of "NoRouteToHost" by SteveLoughran

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The "NoRouteToHost" page has been changed by SteveLoughran:
http://wiki.apache.org/hadoop/NoRouteToHost?action=diff&rev1=3&rev2=4

Comment:
add line on JVM DNS caching

   * The DHCP server is publishing bad routing information.
   * Client and server are on different subnets, and are not set up to talk to each other. This may be an accident, or it is to deliberately lock down the Hadoop cluster. 
   * The machines are trying to communicate using IPv6. Hadoop [[HadoopIPv6|does not currently support IPv6]]
+  * The host's IP address has changed but a long-lived JVM is caching the old value. This is a known problem with JVMs (search for "java negative DNS caching" for the details and solutions). The quick solution: restart the JVMs
   
  These are all network configuration/router issues. As it is your network, only you can find out and track down the problem.