PIM Sparse-Mode | 767• It is recommended that you do not enable IGMP snooping on a PIM-SM snooping-enabled VLANinterface unless until it is necessary for VLAN operation.For information on how to enable PIM-SM snooping and disable PIM DR flooding, refer to PIM-SMSnooping on page 767.PIM-SM SnoopingPIM-SM Snooping is supported on VLAN interfaces on platform: exIn a Layer 2 VLAN, a switch normally floods multicast traffic to all member ports in the VLAN. PIM-SMsnooping is designed to restrict multicast traffic to only the PIM-SM-enabled routers and IGMP hosts thatshould receive the traffic. When PIM-SM snooping is enabled, the switch learns the multicast ports onwhich receivers are listening through PIM hello and PIM-SM join/prune messages, and forwards multicasttraffic only to the VLAN ports connected to valid receivers.Table 34-1. Egress Ports Used for Multicast Traffic with PIM-SM and IGMP SnoopingMulticast Traffic PIM-SM and IGMP Snooping Configuration Egress PortsKnown multicast datapacketsPIM-SM snooping DR flood with IGMP snooping floodPIM-SM snooped VLANsPIM DR portIGMP snooped portsIGMP mrouter portsPIM-SM snooping DR flood with no IGMP snooping floodPIM-SM snooped VLANsPIM DR portIGMP snooped portsIGMP mrouter portsIGMP flood with no PIM-SM snooping DR floodPIM-SM snooped VLANsIGMP snooped portsIGMP mrouter portsNo PIM-SM snooping DR flood and no IGMP snooping floodPIM-SM snooped VLANsIGMP snooped portsIGMP mrouter portsUnknown multicastdata packetsPIM-SM snooping DR flood with IGMP snooping flood PIM DR portPIM-SM snooping DR flood with no IGMP snooping flood PIM DR portIGMP mrouter portsIGMP flood with no PIM-SM snooping DR flood NoneNo PIM-SM snooping DR flood and no IGMP snooping flood IGMP mrouter ports
