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.
Multiple ASes
The following example shows the case of segments spanning across multiple ASes. In most of the cases, the
core tree on the DMZ link is Ingress Replication.
Cisco ASR 9000 Series Aggregation Services Router Multicast Configuration Guide, Release 6.0.x
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