H3C Technologies H3C S10500 Series Switches - Manual (Page 154)

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Admin-scope zones are divided specific to multicast groups. Zone border routers (ZBRs) form the
boundary of the admin-scope zone. Each admin-scope zone maintains one BSR, which serves multicast
groups within a specific range. Multicast protocol packets, such as assert messages and bootstrap
messages, for a specific group range cannot cross the admin-scope zone boundary. Multicast group
ranges that different admin-scope zones serve can be overlapped. A multicast group is valid only within
its local admin-scope zone, and functions as a private group address.
The global scope zone maintains a BSR, which serves the multicast groups that do not belong to any
admin-scope zone.
Relationship between admin-scope zones and the global scope zone
The global scope zone and each admin-scope zone have their own C-RPs and BSRs. These devices are
effective only in their respective zones. That is, BSR election and RP election are implemented
independently within each admin-scope zone. Each admin-scope zone has its own boundary. The
multicast information cannot cross this boundary in either direction. A better understanding of the global
scope zone and admin-scope zones should be based on geographical space and group address range.
1. Geographical space
Admin-scope zones are logical zones specific to particular multicast groups. The multicast packets of
these multicast groups are confined within the local admin-scope zone and cannot cross the boundary of
the zone.
Figure 49 Relationship between admin-scope zones and the global scope zone in geographic space
As shown in Figure 49 , for multicast groups in the same address range, admin-scope zones must be
geographically separated from one another. Namely, a router must not serve different admin-scope
zones. In other words, different admin-scope zones contain different routers, whereas the global scope
zone covers all routers in the PIM-SM/BIDIR-PIM domain. Multicast packets that do not belong to any
admin-scope zones can be transmitted in the entire PIM-SM/BIDIR-PIM domain.
2. Multicast group address ranges
Each admin-scope zone serves specific multicast groups. Usually, these addresses have no intersections.
However, they might overlap one another.