Comment by liveoneggs

One time I was setting up a jboss cluster on vmware boxes - two right next to each other in the rack. JBoss used (uses?) multicast discovery to find the cluster and the VMs on different boxes just couldn't find each other.

Another time I had a backup job using uftp (a multicast file xfer tool) and it was a similar story. Systems literally sitting one rack over couldn't talk.

We involved all of our CC*-certified guys, wasted a week, and eventually just used the explicit command line switches to configure the cluster.

The hardware is not up to the task, physical or virtual, as far as I can tell.