Not tried on 2.12, etc as yet. This is when you specify an incorrect bind address - one that is not available on the target host - and instead of reporting this, JGroups attempts to increase the port number and retry, eventually failing with a port being out of range. This can be very misleading as it leads you to debug conflicting ports, etc., when in fact the problem is a badly configured IP address.

This was reported a few years back on the forums, but I've still seen the issue on JGroups 2.11.