While we don't specifically call it "immediate-leave", a Meraki switch, by default will immediately remove a host from the recipient list as soon as it hears an IGMP leave message from the host. In short, a multicast stream is immediately stopped from being forwarded to a port when an IGMP leave message is received on the port.
Is there any Meraki documentation that states that sates that a Meraki switch, by default, will immediately remove a host from the recipient list as soon as it hears an IGMP leave message? We are having issues with slow switching between Crestron NVX multicast streams. Creston say that it is because Meraki do not support fast-leave/immediate leave. I cannot find any official Meraki documentation to say that it does. Just the odd discussion statement like this one.
I have wiresharks gathered on MS350 switches running MS12.27 that show this is not true. MCAST will continue from the initial address and cause the port to send out both streams until the first stream times out.
This is consistent with Fast-Leave / Immediate-Leave not being enabled or correctly implemented.
In a Crestron NVX system you can turn the stream bandwidth down from 950Mbps to 450Mbps to get around this limitation assuming you are happy with the reduced video quality.