Yes, a unique port for each cluster is definitely recommended. On some platforms (certain Unix versions, some Windows servers) not using a unique port causes weird crosstalk issues as well.
Is the crosstalk a problem for both tcp & udp?
Take a look at the FAQs and wikis on Jgroups' site for details. It's pretty well documented there.
I didn't see anything relevant, instead I found the following two articles:
Based on those articles, the JGroups DOES support shared transport. Could you please get Bela or Vladimir (who is the author of the first article) to comment? Is there any performance issue with the shared transport?
Shared transport works particularly well in AS environments where you have multiple Infinispan Cache Manager's in action. JBoss Application Server uses this. I'd suggest looking into what the JBoss AS guys did for AS6 if you can't wait for Bela/Vladimir.
Even thouhg http://community.jboss.org/docs/DOC-12460 is oriented for JBoss Application Servers, the concepts are the same and you need to apply the same rules to the JGroups channels backing Infinispan if you wanna keep them separate.
Thanks for the response. I got a response from Bela on JGroups forum, and clear about it.