Are there any negative effects from this type of setup?

We chose only to change partition names because we already had a mechanism that would ensure those names were not repeated (the unique naming of our clusters).

If I were to change the port number, what would be the benefit (if any) in having a different partition name?

I should have asked if there were any negative effects other than the use of CPU to reject the message from different parititions?

Furthermore to solve the problem of automatic port number selection (so we can do this programatically), is there any example JBoss/JGroups code that we could use to test to see if a randomly selected port number was in use for multicasting?

We are considering doing something like this or just using some kind of hash to (mostly) guarantee uniqueness.

I meant that the random selection idea would select the port for a cluster of nodes, not just a particular node, but it would have to exist at a "cluster" startup level not a "node" startup level.

If I utilized ${system property name} replacement in the file, and then passed the same port for a multicast configuration to the VM as a system property for every node in the cluster, it seems to me it would work. Currently, we are doing that for the cluster partition name, but you are right, I have include that substitution in several different places. The port number would be a single substitution in a single file.

Does the cited example in UDP.java easily map to multicast configurations too, so I could test random or hash-selected cluster multicast port numbers for listeners?