multicast problem (version 8.5) igmp

[bouletbill]

hi,
i would like to use videoserver on the network with multicast.
my network is cisco (with router igmp, switch cgmp,..) already use for multicast use.

i have a server and a client . i would like to establish in multicast mode a connection on the network.
when i run client (see on my sniffer : igmp v3 membership report igmp group 224.0.0.22 contained the group 239.x.x.x). but when i run server (nothing on my sniffer.).
so how can i configure the server for multicast use ?
the only case where , it's ok is one the same switch (but no mechanism of report igmp).

thanks to help me