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.
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 between trees. PIM-SM uses a bootstrap router (BSR), which advertises information to other multicast routers about the RP. In a given network, a set of routers can be administratively enabled as candidate bootstrap routers. If it is not apparent which router should be the BSR, the candidates flood the domain with advertisements. The router with the highest priority is elected. If all the priorities are equal, then the candidate with the highest IP address becomes the BSR. PIM-SM is defined in RFC 4601.
In order to configure and use PIM-SM, set the switch B,C,D as RP-candidate and BSR-candidate. Switch B will become the BSR because it has the highest priority. Switch D will become the RP after RP election.
For more information, see the following support articles:
- How do I configure Protocol-Independent Multicast Sparse Mode (PIM-SM) using CLI commands on my managed switch?
- How do I configure Protocol-Independent Multicast Sparse Mode (PIM-SM) using the web interface on my managed switch?
- What is Protocol-Independent Multicast (PIM) and how does it work with my managed switch?
This article applies to the following managed switches and their respective firmware:
- M5300 - firmware version 10.0.0.x
-
- M5300-28G (GSM7228S)
- M5300-5G (GSM7252S)
- M5300-28G3 (GSM7328Sv2h2)
- M5300-52G3 (GSM7352Sv2h2)
- M5300-28G_POE+ (GSM7228PSv1h2)
- M5300-52G-POE+ (GSM7252PSv1h2)
- M5300-28GF3 (GSM7328FSv2)
- XSM7224S - firmware version 9.0.1.x (license required to support the feature described in this article)