Do all ethernet switches support multicast?

Solution 1:

Yes, even unmanaged "bargain" switches will likely have some minimal support for multicast, to the extent that a host connected to the switch will be able to receive a multicast stream.

Look at the switch's technical specs for a feature called IGMP snooping. This allows the switch to learn which ports actually want to subscribe to a multicast group, so it can forward it to only those who want it (which is the whole point of multicast). Without it, multicast will probably still work, but the switch will treat it as broadcast traffic and flood the multicast stream to all ports.

Solution 2:

Simple switches treat multicast like broadcast[*], as least as far as I have seen. Therefore, multicast will reach its destinations but may cause unnecessary traffic since it's forwarded to unsubscribed nodes as well. Depending on used bandwidth, usually this is not really a problem.

[*] When a switch forwards a frame with an unknown destination address, it simply floods the frame to all ports except the one it was received from - basically acting like a repeater hub. Dumb switches don't understand multicast, so the address is always unknown (it's only used as destination, never as source; the switch's MAC table is updated by source addresses).