I have a somewhat unique application that uses Multicast for dozens of client devices to send data to a small group of servers.
The client devices use 239.192.1.1 as the destination IP, and the servers are members of this group. The servers are connected to a layer-2 switch. This switch connects to 2 switches (Cisco Catalyst 6500 and 3560) running IP routing and PIM sparse-mode Each router has an RP set. These switches each have a unique subnet behind them, with these client devices connected.
The problem I need help with is this:
When I only have the clients on switch A powered on, multicast messages flow downstream towards the servers, through the layer 3 switch. When I power on the second group of devices on switch B, there seems to be an RP designated router 'election' to the switch with the higher IP on the server vlan (in this case, the 3560E). Once this happens, the group of devices on switch A can no longer get their multicast messages forwarded thru switch A, only devices on switch B are able to do this. If I shut down switch B, the change is not reversed until I shutdown the both interfaces (vlan101, 111) on the 3560 and reboot the devices on switch A. This puts it back to the original state with clients on switch A communicating, and switch B shutdown. Bringing the interfaces on the 3560 up repeats the problem.
We also tried getting the clients on switch B to send to a different group (239.192.1.3), that didn't work either, so there must be some problem relating to the RP, I think.
What I'm not sure of is if there is something I can do to keep both groups of client devices 'online' and sending messages to the same Multicast group via two separate paths, or if that is even my problem. Any ideas? Thank you very much.
