Multicast / TIBCO problems

[Maurizio Fulli]

Hi guys,
there are three partions on a Superdome (for convention A - B - C ), that have configurated a Tibco Rendezvous, that comunicate trought an udp bus adapter. Every machines lanch two daemons, one for a data comunication, and one for the monitoring purpose.
When the daemons starts, it opens a tcp port for comunicate with the its applications, that in is turn opens a udp bus with a multicast address: 239.1.0.1 for the data , and 239.1.0.74 for the monitoring.
The 3 machines have the same level patches,the same network configuration, the same lan driver.
I've used a sniffer for trace the multicast traffic, for the data channel, all works good, but isn't so for the monitoring traffic.
"B" and "C" exchange themselves data monitoring, on multicast address.
"A" try to sends and receives that; on the trace files, i look that the multicast address is active, but it does not succed to go out, "A" has an inbound and outbound traffic on multicast address, but if i put in listening on the "B", i don't receive anything!
I have had the net apparatuses checked, but there is no filtering on the 239.1.0.74 address, i supposed that tibco opens a tcp port, so opens a bus adapter on multicast address, tries to do traffic (this is able to go out of the net card, in fact there are tracks on the trace files) but doesn't succeed to attach on the udp bus adapter.
The strange thing, it is that for the data traffic everything works. The Tibco configuration is ok, (it is very simple), the multicast configuration on the lan is ok, and I am not able to understand where the problem is!
I've used the nettl command for trace, lanadmin and lanshow for see the details of lan configuration, netstat -g and -p udp for see the network details.
In attach there is a part of a trace file, please help me!!! I have arrived to a blind alley!
Thanks a lot
regards
Maurizio