PIM Sparse-Mode | 769• In the downstream PIM TIB, states and timers are maintained for each VLAN and member port. Thedownstream outgoing-interface timers for each valid (*,G) and (S,G) entry are started for each VLAN/port and upstream neighbor combination: (port,*,G,neighbor) or (port,S,G,neighbor), where port is adownstream port and neighbor is the upstream neighbor.• A timer is removed when a timer times out or a prune message is received for a specific VLANmember port.• PIM-SM snooping does not use the unicast Real Time Monitor (RTM) to forward snoopedpackets.• All multicast route and router information is timed-out based on the hold-time indicated in the PIMhello and PIM-SM join/prune control packets.Configuration Notes and RestrictionsThe following conditions apply when you configure and use PIM snooping on a switch:• PIM-SM snooping is deployed in a Layer 2 environment and is mutually exclusive with PIM multicastrouting. If you enable PIM-SM snooping, you cannot enable PIM-SM or PIM-DM. If you enablePIM-SM snooping, you cannot enable PIM-SM or PIM-DM• PIM-SM snooping is supported with IGMP snooping, and forwards the IGMP report on the port thatconnects to the PIM DR.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 the egress ports used for outgoing multicast traffic when you enable PIM-SMsnooping and IGMP snooping at the same time on a VLAN interface, see PIM-SM and IGMP Snoop-ing: Usage Notes on page 766.• PIM-SM snooping listens to PIM hello and PIM-SM join and prune messages while maintaining theVLAN- and port-specific information in multicast packets that are snooped.
