Hello again,
unfortunately we are unable to reproduce that issue :( We don't know what is causing it. All 4 servers are currently connected to only one switch.
What do you mean with "you could try enabling tracing" - is this some configuration on JBoss? The messages are sent only from the 4th app server with ip 10.21.1.57. It's UDP traffic destined to the multicast group 228.1.2.13.
Do you need any specific part of configuration, because I don't really got that question too :(
Thank you so much, I really appraciate your time and effort!