 <p>The first seed node is special, as documented in the Cluster documentation: <a href="http://doc.akka.io/docs/akka/snapshot/java/cluster-usage.html" rel="nofollow">http://doc.akka.io/docs/akka/snapshot/java/cluster-usage.html</a></p> <p>It must be the same 1st configured node on all nodes, in order for all of them to be really sure that they join the same cluster.</p> <p>Quote:</p> <p>The seed nodes can be started in any order and it is not necessary to have all seed nodes running, but the node configured as the first element in the seed-nodes configuration list must be started when initially starting a cluster, otherwise the other seed-nodes will not become initialized and no other node can join the cluster. <strong>The reason for the special first seed node is to avoid forming separated islands when starting from an empty cluster.</strong> It is quickest to start all configured seed nodes at the same time (order doesn't matter), otherwise it can take up to the configured seed-node-timeout until the nodes can join.</p> <p>Once more than two seed nodes have been started it is no problem to shut down the first seed node. If the first seed node is restarted, it will first try to join the other seed nodes in the existing cluster.</p>