Administrative Scoping Overview - HP MSR2003 Configuration Manual

Figure 38 RPT building at the multicast source side
As shown in
4. When a multicast source sends multicast packets to the multicast group G, the DF in each subnet
unconditionally forwards the packets to the RP.
5. The routers along the path from the source's directly connected router to the RP constitute an RPT
branch. Each router on this branch adds to its forwarding table a (*, G) entry, where the asterisk
(*) represents any multicast source.
After a bidirectional RPT is built, the multicast sources send multicast traffic to the RP along the source-side
RPT. When the multicast traffic arrives at the RP, the RP forwards the traffic to the receivers along the
receiver-side RPT.
IMPORTANT:
If a receiver and a source are at the same side of the RP, the source-side RPT and the receiver-side RPT
might meet at a node before reaching the RP. In this case, the multicast packets from the multicast source
to the receiver are directly forwarded by the node, instead of by the RP.

Administrative scoping overview

Typically, a PIM-SM domain or a BIDIR-PIM domain contains only one BSR, which is responsible for
advertising RP-set information within the entire PIM-SM domain or BIDIR-PIM domain. The information
about all multicast groups is forwarded within the network that the BSR administers. This is called the
"non-scoped BSR mechanism."
Administrative scoping mechanism
To implement refined management, you can divide a PIM-SM domain or BIDIR-PIM domain into a
global-scoped zone and multiple administratively-scoped zones (admin-scoped zones). This is called the
"administrative scoping mechanism."
The administrative scoping mechanism effectively releases stress on the management in a single-BSR
domain and enables provision of zone-specific services through private group addresses.
Figure 38, the process for building a source-side RPT is relatively simple:
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