Symptoms

Testing multicast connectivity (example tool: http://download.oracle.com/otn/java/coherence/coherence-331.zip) results in one of the nodes successfully receiving multicast messages, while the other(s) fail to.

Diagnosis

Setting the multicast group address between 224.0.0.1 and 224.0.1.0 will make the connectivity work, but addresses outside this range fail to work.

Cause

Some routers/network elements filter globally-scoped multicast addresses, but let the reserved range through.

Workaround

Use the reserved range, however this may be more polluted in various networks or not available. Please contact your network administrators on picking the range.

Resolution

Allow multicast traffic on the desired range/address, contact your network administrators.