Operating rules and recommendations

Guideline for configuring C-RPs and BSRs

Routers in a PIM-SM domain should usually be configured as both C-RPs and candidate BSRs; this can reduce some overhead traffic.

The SPT policy should be the same for all RPs in a domain.

Allowing some RPs to remain configured to implement SPTs while configuring other RPs in the same domain to force RPT use can result in unstable traffic flows. (Use the [no] ip pim-sparse spt-threshold command to change between SPT and RPT operation on each router.)

Application of RPs to multicast groups.

In a PIM-SM domain, a given multicast group or range of groups can be supported by only one RP. (Typically, multiple C-RPs in a domain are configured with overlapping coverage of multicast groups, but only one such candidate will be elected to support a given group.)

Ensuring that the C-RPs in a PIM-SM domain cover all desired multicast groups.

All of the multicast groups you want to allow in a given PIM-SM domain must be included in the aggregate of the multicast groups configured in the domain's C-RPs. In most cases, all C-RPs in a domain should be configured to support all RP groups (the default configuration for a router enabled as a C-RP.) This provides redundancy in case an RP becomes unavailable. (If the C-RP supporting a particular multicast group becomes unavailable, another C-RP is elected to support the group as long as there is redundancy in the C-RP configuration for multiple routers.) Note that is cases where routers are statically configured to support a specific group or range of groups, the C-RP prioritization mechanism allows for redundant support.


These two features cannot both be enabled on the same router at the same time.

Supporting PIM-SM across a PIM Domain.

To properly move multicast traffic across a PIM-SM domain, all routers in the domain must be configured to support PIM-SM. That is, a router without PIM-SM capability blocks routed multicast traffic in a PIM-SM domain.