When you say you are adding a second virtual host be sure you aren't adding another mod_cluster virtual; you only need one of those (ie only one listening on, say, port 6666). Both JBoss clusters should talk back to that virtual. To be 100% sure the jboss nodes are all hitting the same port start them up with: jboss.modcluster.proxyList=1.2.3.4:6666,1.2.3.5:6666 (replacing witht he correct IPs of course). This will avoid the multicast and let you know what's up. Post your mod_cluster virtual and the two apache virtuals too if you like!