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Multicast group ranges within different admin-scoped zones can be overlapped. A multicast group is
valid only within its local admin-scoped zone, and functions as a private group address.
The global-scoped zone maintains a BSR, which serves the multicast groups that do not belong to any
admin-scoped zone.
Relationship between admin-scoped zones and the global-scoped zone
The global-scoped zone and each admin-scoped zone have their own C-RPs and BSRs. These devices are
effective only on their respective zones, and the BSR election and the RP election are implemented
independently. Each admin-scoped zone has its own boundary. The multicast information within a zone
cannot cross this boundary in either direction. You can have a better understanding of the global-scoped
zone and admin-scoped zones based on geographical locations and multicast group address ranges.
•
In view of geographical locations:
An admin-scoped zone is a logical zone for particular multicast groups. The multicast packets for
such multicast groups are confined within the local admin-scoped zone and cannot cross the
boundary of the zone.
Figure 27
Relationship in view of geographical locations
As shown in
, for the multicast groups in a specific group address range, the
admin-scoped zones must be geographically separated and isolated. A router cannot belong to
multiple admin-scoped zones. In other words, different admin-scoped zones contain different
routers. However, the global-scoped zone includes all routers in the PIM-SM domain or BIDIR-PIM
domain. Multicast packets that do not belong to any admin-scoped zones are forwarded in the
entire PIM-SM domain or BIDIR-PIM domain.
•
In view of multicast group address ranges:
Each admin-scoped zone serves specific multicast groups, of which the multicast group addresses
are valid only within the local zone. The multicast groups of different admin-scoped zones might
have intersections. All the multicast groups other than those of the admin-scoped zones are served
by the global-scoped zone.