JBoss AS uses JGroups internally to create cluster groups. If you are having problems with your cluster communication, it would be easy to check JGroups configuration first. A little “how to” can be found at JBoss Wiki:
Testing whether nodes find each other, without Jboss AS.
http://www.jboss.org/community/wiki/TestingJBoss
Another useful diagnosis tool is the “probe” script (it can be found at jboss/bin directory)
$: ./jboss-4.2.3.GA.test/bin/probe.sh -timeout 500 -query jmx -query props
