NOTE:
In a PIM-SM domain where there are overlapping ranges of multicast groups configured on the C-
RPs, discrete ranges of these groups are assigned to the domain's C-RPs in blocks of sequential
group numbers. The number of multicast groups in the blocks assigned within a given domain is
determined by the
bsr-candidate hash-mask-length
value (range=1 to 32) configured on the elected BSR for the domain. A higher value means fewer
sequential group numbers in each block of sequential group numbers, which results in a wider
dispersal of multicast groups across the C-RPs in the domain.
As indicated above, multiple C-RPs can be configured to support the same multicast group(s.) This is
the generally recommended practice and results in redundancy that helps to prevent loss of support
for desired multicast groups in the event that a router in the domain becomes unavailable.
Configuring a C-RP to support a given multicast group does not ensure election of the C-RP to
support that group unless the group is excluded from all other RPs in the domain.
Also, within a PIM-SM domain, a router can be configured as a C-RP available for a given multicast group or
range of groups and as the static RP for a given multicast group or range of groups. The recommended practice
is to use C-RPs for all multicast groups unless there is a need to ensure that a specific group or range of groups
is always supported by the same routing switch. See
Redundant Group Coverage Provides Fault-Tolerance
If a C-RP elected to support a particular multicast group or range of groups becomes unavailable, the router is
excluded from the RP-set. If the multicast group configuration of one or more other C-RPs overlaps the
configuration in the failed RP, then another C-RP is elected to support the multicast group(s) formerly relying on
the failed RP.
Static RP (static RP)
General application
Like C-RPs, static RPs control multicast forwarding of specific multicast groups or ranges of contiguous groups.
However, static RPs are not dynamically learned, and increase the configuration and monitoring effort needed to
maintain them. As a result, static RPs are not generally recommended for use except where one of the following
conditions applies:
• It is desirable to designate a specific router interface as a backup RP for specific group(s.)
• Specific multicast groups are expected, and a static RP would help to avoid overloading a given RP with a high
volume of multicast traffic.
• A C-RP for the same group(s) is less reliable than another RP that would not normally be elected to support
the group(s.)
• Tighter traffic control or a higher priority is desired for specific multicast groups
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Aruba 3810 / 5400R Multicast and Routing Guide for ArubaOS-
Switch 16.08
