Multicast - PIM Snooping

In a network where you have a layer two switch connected to Multicast routers, all multicast traffic is flooded to all multicast router ports, even if there are no multicast receivers behind a router.

When you enable PIM snooping, the switch will learn which multicast router ports should receive traffic by looking at PIM hello, join, prune, and designated forward election messages.

PIM snooping should not be confused with IGMP snooping.

Links

https://networklessons.com/cisco/ccie-routing-switching-written/multicast-pim-snooping