224.0.0.0/4
In non-default candidate configurations, an RP allows up to four ranges of contiguous multicast groups, and/or
individual multicast groups, or both. For example:
RP candidate configuration
Supported range of multicast groups
235.0.240.0/12
235.0.240.1 — 235.0.255.255
235.0.0.1/28
235.0.0.1 — 235.0.0.15
235.0.0.128/32
235.0.0.128 only
235.0.0.77/32
235.0.0.77 only
NOTE:
If a given multicast group is excluded from all RPs in a given domain, then that group will not
be available to the multicast receivers connected in the domain.
For more on this topic, see
Configuring C-RPs on PIM-SM routers
C-RP election
Within a PIM-SM domain, different RPs support different multicast addresses or ranges of multicast addresses.
(That is, a given PIM-SM multicast group or range of groups is supported by only one active RP, although other C-
RPs can also be configured with overlapping or identical support.)
A C-RP's group-prefix configuration identifies the multicast groups the RP is enabled to support.
If multiple C-RPs have group-prefixes configured so that any of these RPs can support a given multicast group,
then the following criteria are used to select the RP to support the group:
Procedure
1.
The C-RP configured with the longest group-prefix mask applicable to the multicast group is selected to
support the group. Step 2 of this procedure applies if multiple RP candidates meet this criterion.
2.
The C-RP configured with the highest priority is selected. Step 3 of this procedure applies if multiple RP
candidates meet this criterion.
3.
A hash function (using the configured
bsr-candidate hash-mask-length
value) generates a series of
mask length values that are individually assigned to the set of eligible C-RPs. If the hash function matches a
single RP candidate to a longer mask length than the other candidates, that candidate is selected to support
the group. Apply step 4 of this procedure if the hash function matches the longest mask length to multiple RP
candidates.
4.
The C-RP having the highest IP address is selected to support the group.
Chapter 4 PIM-SM (Sparse Mode)
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