Does this work?
-b 0.0.0.0 -Djgroups.bind_addr=192.168.7.1
If not, check the server.log files, JGroups logs to STDOUT information about how it's binding sockets; you can see what interface it's trying to use.
If it's using the correct interface, then try the diagnostic tests linked to in the "Further troubleshooting" section of http://community.jboss.org/wiki/TestingJBoss . Make sure you test the same multicast address and ports you've configured JBoss AS to use; I've seen machines configured to route part of the class D address space over eth0 and the rest over eth1.
OK... I didn't try your way exactly, but did use something like it. An observation (over the past week or so of beating my head against this wall and reading everything I can find) finally clicked in that for most of the places where people appear to succeed, they appear to set things in the command line options.
Soooo I created a command line feeder which looks very like this - experimenting with an unmodified "all" config so that I could bounce the machine faster and cleaner ( our fully installed system is a lot heavier ). The names have been changed because I am a paranoid sort of guy.
run.sh -b 0.0.0.0 -g MyCluster -c myCluster -u 126.96.36.199 -Dbind.address=192.168.7.1 -Dhornetq.remoting.netty.host=192.168.7.1
-and with a small hint to hornetq in its own config file, it all appears to work properly. I say appears because I only managed to get to this point yesterday and we're still seeing if it does actually work.
The annoying thing about the environment we got was that it wasn't built this way on-purpose but it is about as difficult as any can be for this purpose.
Now all I can observe leads me to the belief that setting this up through the system properties ALMOST works... the logs all say its all good... but it isn't, because it always comes back as the only server in the cluster... but something is not reading one of the properties unless it is set through the command line. What, where, how I am not interested in. I found an answer. I'll live with the funky command line kluge :-)
I'd vastly prefer that the apps developers got their stuff to work on 5.1.GA and let me work with the more coherent system.... not quite yet. I am supposed to get that for our next installation, but that is then and this is now.
I suspect, because of changes used when things finally worked, that there was something about the default multicast address. I finally used a simple client server to verify multicast working. The other possibility is that the admin I was working with had left multicast disabled and simply re-enabled it when I mentioned I was looking at it . One can never be sure unless they give you root. :-)