2.2.c Explain PIM snooping

In networks where a Layer 2 switch interconnects several routers, the switch floods IP multicast packets on all multicast router ports by default, even if there are no multicast receivers downstream. With PIM snooping enabled, the switch restricts multicast packets for each IP multicast group to only those multicast router ports that have downstream receivers joined to that group. When you enable PIM snooping, the switch learns which multicast router ports need to receive the multicast traffic within a specific VLAN by listening to the PIM hello messages, PIM join and prune messages, and bi-directional PIM designated forwarder-election messages.

show ipv6 snooping command provides information about an interface on which both the Neighbor Discovery Inspection and RA Guard features are configured.

Adam, Paul (2014-07-12). All-in-One CCIE V5 Written Exam Guide (Kindle Locations 2098-2104).  . Kindle Edition.

http://www.cisco.com/c/en/us/td/docs/switches/lan/catalyst6500/ios/12-2SX/configuration/guide/book/snooppim.html