Protocol Independent Multicast (PIM) snooping restricts multicast traffic on interfaces that are connected to multicast routers; Internet Group Management Protocol (IGMP) snooping does not. IGMP snooping restricts multicast traffic only on interfaces that are connected to host devices.

IGMP snooping does not require that PIM snooping also be enabled. However, PIM snooping requires that IGMP snooping be enabled. IGMP snooping enables switches to listen to IGMP traffic and forward multicast traffic only to ports from which an IGMP report has been received. IGMP reports are sent from multicast receivers that want to receive traffic from a multicast group. When an IGMP report is received on a port, the switch adds the port number to the list of ports that should receive traffic for that multicast group. When an IGMP leave message is received on a port, the switch sends an IGMP query to determine whether any interested multicast receivers remain on the port.

IGMP snooping is enabled on Cisco switches by default. You can globally disable IGMP snooping on a switch by issuing the no ip igmp snooping command from global configuration mode. Alternatively, you can disable IGMP snooping on a particular virtual LAN (VLAN) by issuing the no ip igmp snooping command from interface configuration mode for that VLAN. When IGMP snooping is disabled, switches will flood multicast traffic to every port in every VLAN. To reenable IGMP snooping, you should issue the ip igmp snooping command from global configuration mode or from interface configuration mode.

PIM snooping is disabled on Cisco switches by default. You can globally enable PIM snooping on a switch by issuing the ip pim snooping command from global configuration mode. Alternatively, you can enable PIM snooping on a particular VLAN by issuing the ip pim snooping command from interface configuration mode for that VLAN. To disable PIM snooping, you should issue the no ip pim snooping command from global configuration mode or from interface configuration mode.

Neither PIM snooping nor IGMP snooping restricts IPv6 multicast traffic. To restrict IPv6 multicast traffic, you need to enable Multicast Listener Discovery (MLD) snooping. Similar to how IGMP snooping forwards IPv4 multicast traffic, MLD forwards IPv6 multicast traffic only to ports from which an MLD report has been received. MLD is enabled by default. When MLD is enabled, MLD messages are sent with a timetolive (TTL) value of 1, which means that an MLD message is sent only to the next hop. You can globally disable MLD snooping on a switch by issuing the no ipv6 mld snooping command from global configuration mode.

Alternatively, you can disable MLD snooping on a particular VLAN by issuing the no ipv6 mld snooping command from interface configuration mode for that VLAN. When MLD snooping is disabled, switches will flood IPv6 multicast traffic to every port in every VLAN. To re-enable MLD snooping, you should issue the ipv6 mld snooping command from global configuration mode or from interface configuration mode.