4000 Router Series IP Multicast Configuration Guide

Administrative scoping overview

Typically, a PIM-SM domain contains only one BSR, which is responsible for advertising RP-set

information within the entire PIM-SM 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 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.

Admin-scoped zones are divided for multicast groups. Zone border routers (ZBRs) form the boundary of

an admin-scoped zone. Each admin-scoped zone maintains one BSR for multicast groups within a

specific range. Multicast protocol packets, such as assert messages and BSMs, for a specific group range

cannot cross the boundary of the admin-scoped zone for the group range. Multicast group ranges that

are associated with different admin-scoped zones can have intersections. However, the multicast groups

in an admin-scoped zone are valid only within the local zone, and theses multicast groups are regarded

as private group addresses.

The global-scoped zone maintains a BSR for the multicast groups that do not belong to any

admin-scoped zones.

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

take effect 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.