Test multicast with the generator and receiver
Multicast is miserable to test by hand. netplex. ships a matched tool pair: the Multicast Generator sends to a group address you choose, the Multicast Receiver joins groups and reports what actually arrives - IGMP and all. Wire them across whatever topology you are testing and see where multicast dies.
Both tools live in the palette's netplex. group. Here the generator and receiver share one link - in a real test you would put your switches, IGMP snooping and routers between them.
Double-click the generator: pick the group address (239.x.x.x), port, rate and TTL, then start the stream.
Double-click the receiver and join the same group. It reports joined groups and per-group packet counts as traffic arrives - if the counter stays at zero, something between the two is eating your multicast (IGMP snooping without a querier is the usual suspect).
Add a packet capture on any link in the path to see the IGMP joins and the stream itself on the wire. The fabric never injects its own traffic (zero-injection guarantee), so every multicast packet you capture is yours.