PIM-SM operation

In a given PIM-SM domain, routers identified as DRs, RPs, and a BSR participate in delivering multicast traffic to the IP multicast receivers that request it. This approach avoids the flooding method of distributing multicast traffic (employed by PIM-DM) and is best suited for lower bandwidth situations.

The software supports the following operation to enable multicast traffic delivery within a PIM-SM domain:

• From a pool of eligible DR candidates in each VLAN, one DR is elected for each VLAN interface having at least one PIM-SM router. In a multinetted domain, this DR supports multicast traffic from a source on any subnet in the VLAN.

• From a pool of eligible BSR candidates in the domain, one BSR is elected for the entire domain.

• From a pool of eligible C-RPs, one is elected to support each multicast group or range of groups allowed in the domain, excluding any group supported only by static RPs. The multicast groups allowed in the domain are determined by the aggregation of the groups allowed by the individually configured RPs and any static RPs. (Note that RP-Cs and static RP’s can be configured with overlapping support for a given set of multicast groups.)