Netgear M4100-26G Software Administration Manual - Page 460

ProSafe M4100 and M7100 Managed Switches PIM-SM Protocol-independent multicast sparse mode (PIM-SM) is used to efficiently route multicast traffic to multicast groups that can span wide area networks where bandwidth is a constraint. Source IP 192.168.1.1 Subnet 192.168.1.0/24 Switch A Port 1/0/13 Port 1/0/1 Port 1/0/9 Port 1/0/10 Subnet 192.168.3.0/24 Port 1/0/11 Switch B Subnet 192.168.5.0/24 Subnet 192.168.2.0/24 Switch D Port 1/0/21 Port 1/0/24 Port 1/0/22 Port 1/0/22 Subnet 192.168.6.0/24 Port 1/0/21 Switch C Subnet 192.168.4.0/24 Host IP 192.168.4.2 Figure 46. PIM-SM PIM-SM uses shared trees by default and implements source-based trees for efficiency; it assumes that no hosts want the multicast traffic unless they specifically ask for it. It creates a shared distribution tree centered on a defined rendezvous point (RP). Traffic from this source is relayed to the receivers. Senders first send the multicast data to the RP, which in turn sends the data down the shared tree to the receivers. Shared trees centered on an RP do not necessarily provide the shortest, most optimal path. In such cases PIM-SM provides a means to switch to more efficient source-specific trees. A data threshold rate is defined for toggling 460 | Chapter 28. PIM