Segmented Multicast - Examples - Cisco ASR 9000 Series Configuration Manual

Implementing Layer-3 Multicast Routing on Cisco IOS XR Software
Segmented Multicast - Overview

Segmented Multicast - Examples

Segmented Core Single AS
In the following figure, a single AS runs OSPF in the core. The core has a Backbone Area (0) and non-zero
Areas for each site. A path from an Ingress PE to an Egress PE traverses through an Ingress non-zero Area
(iPE to iABRs), Area 0 (iABR to eABRs), and the Egress non-zero Area (eABR to ePEs). In the following
figure, only the PEs and the border routers (ABRs) are used, however, there can be multiple P-routers between
the PE and ABR or between ABRs.
With Segmented Multicast, when there is a need to build an I-PMSI or S-PMSI tunnel between iPE and ePE,
the tunnel is built with multiple core-trees. The iPE builds a core-tree to iABRs, and later the iABR builds a
separate core-tree to the set of eABRs. The iABR then stitches the two core-trees, such that packets arriving
on the non-zero Area core-tree will be forwarded out of the Area-0 core-tree. The Egress ABR (eABR) also
performs a similar stitching between two core-trees to forward traffic to the Egress PEs (ePEs).
The example shows OSPF areas, however, the same concept is supported on IS-IS IGP as well.
Cisco ASR 9000 Series Aggregation Services Router Multicast Configuration Guide, Release 6.0.x
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