We should investigate dropping that flag - how will connections to jmx servers and the agent/server communication work? This flag prevents simultaneous usage of IPv6 and IPv4 : See Bug 809721 and Bug 809125 ------ from rhq-devel: Interestingly enough, this bug itself may have been solved, but we may be running into a different one: the -Djava.net.preferIPv4Stack=true property now looks like the bad guy: snert:/im/rhq/modules/enterprise/agent/target/rhq-agent hrupp$ java -version java version "1.6.0_31" Java(TM) SE Runtime Environment (build 1.6.0_31-b04-415-11M3635) Java HotSpot(TM) 64-Bit Server VM (build 20.6-b01-415, mixed mode) snert:/im/rhq/modules/enterprise/agent/target/rhq-agent hrupp$ echo $RHQ_AGENT_JAVA_OPTS -Xmx320m -agentlib:jdwp=transport=dt_socket,address=8788,server=y,suspend=n snert:/im/rhq/modules/enterprise/agent/target/rhq-agent hrupp$ bin/standalone.sh Listening for transport dt_socket at address: 8788 Starting the plugin container. Loading plugins ...Loaded plugin: JBossAS7 ...Loaded plugin: JMX ...Loaded plugin: Platforms Ready. [0]:0 > disc s Discovery took: 1021ms [Resource[id=-3, uuid=a7d94d2d-944d-4c12-881a-73bef576a3c7, type={JBossAS7}JBossAS7 Standalone Server, key=/devel/jboss-eap-6.0/standalone, name=EAP (::1:9990), parent=snert, version=EAP 6.0.0.Beta2]] [1]:0 > avail -3 EAP (::1:9990)( -3 ):UP [2]:0 > quit Terminating .. Shutting down ... snert:/im/rhq/modules/enterprise/agent/target/rhq-agent hrupp$ export RHQ_AGENT_JAVA_OPTS="$RHQ_AGENT_JAVA_OPTS -Djava.net.preferIPv4Stack=true" snert:/im/rhq/modules/enterprise/agent/target/rhq-agent hrupp$ echo $RHQ_AGENT_JAVA_OPTS -Xmx320m -agentlib:jdwp=transport=dt_socket,address=8788,server=y,suspend=n -Djava.net.preferIPv4Stack=true snert:/im/rhq/modules/enterprise/agent/target/rhq-agent hrupp$ bin/standalone.sh Listening for transport dt_socket at address: 8788 Starting the plugin container. Loading plugins dis...Loaded plugin: JBossAS7 ...Loaded plugin: JMX ...Loaded plugin: Platforms Ready. [0]:0 > disc s Discovery took: 1172ms [Resource[id=-3, uuid=5a2f33c7-62a3-434a-95cc-c24aa319725f, type={JBossAS7}JBossAS7 Standalone Server, key=/devel/jboss-eap-6.0/standalone, name=EAP (::1:9990), parent=snert, version=EAP 6.0]] [1]:0 > avail -3 EAP (::1:9990)( -3 ):DOWN