There is IP based multicast (224.x IP addresses). This layer is managed by the routers knowing what downstream routers need copies of the traffic and sends it to all of them
There is ethernet link-layer multicast (a '1' in the least significant bit of the first byte of the MAC address, i.e. 01:00:00:00:00:00), traffic to these MAC addresses get handled by the ethernet switch.
These two can be used in combination with each other, but you can use the link-layer multicast with any IP address (and with no modification to the sending or recieving software), and I assume that you could use the IP based multicast without using the link-layer multicast, but I also wouldn't be surprised to learn that most of the time things default to using link-layer multicast if you are using the IP multicast range.
I also think that you will find that even the rather cheap switches handle link-layer multicast nowdays.
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