I had this issue the other day. It has do do with machines with multiple NICs/IPAddresses. Edit the following files: $JBOSS_HOME/server/yourserver/deploy/cluster-service.xml $JBOSS_HOME/server/yourserver/deploy/tc5-cluster.sar/META-INF/jboss-service.xml Look for this comment where the Mutlicast settings are located (PartitionConfig and ClusterConfig respectively). | <!-- | The default UDP stack: | - If you have a multihomed machine, set the UDP protocol's bind_addr attribute to the | appropriate NIC IP address, e.g bind_addr="192.168.0.2". | - On Windows machines, because of the media sense feature being broken with multicast | (even after disabling media sense) set the UDP protocol's loopback attribute to true | --> | As suggested by the comment, add the bind_addr="" attribute to the tag and specify the one(1) IP Address you want to bind to for multicasting. View the original post : http://www.jboss.com/index.html?module=bb&op=viewtopic&p=4016400#... Reply to the post : http://www.jboss.com/index.html?module=bb&op=posting&mode=reply&a...