Thanks Shreedhar for your prompt response.
Since the basic multicast wasn't working (diagnosed using JGroups test), I worked with our network engineer to make sure our routers are configured to allow multicast traffic. It turns out that the router was partially configured, it wasn't allowing multicast group to be formed. We turned the PIM module on (we have a cisco router) and tested the multicast traffic using the same test program and it worked. Next I brought up my cluster and ran through my earlier scenario and it worked like a champ this time.
I think with multicast/clustering we should have set of pointers and trouble shooting hints: start from basic and work our way up the stack. Clustering does complicate things a bit because you have DAS, node agents, Glassfish AS instances and then hardware servers. Figuring out sequence of steps to troubleshoot where the problem might becomes a challenge even in a simple scenario like mine (1 DAS, 2 hardware servers, 2 node agents, 4 instances).
Thanks for your help.
--
Sanjay
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