Discussion

AS 65500
RouterB
192.168.12.1
10.0.22.2/24
10.0.22.1/24
RouterC
192.168.11.1
AS 65520
RouterA
RouterD
192.168.13.1 10.0.21.2/24 10.0.29.1/24 192.168.14.1
10.0.21.1/24 10.0.29.2/24
10.0.16.1/24
10.0.24.2/24
10.0.15.2/24 10.0.31.1/24
10.0.16.2/24 Multicast link
10.0.15.2/24
Router G (RP)
192.168.19.1
10.0.22.2/24
10.0.24.1/24
Router H (RP)
192.168.18.1
10.0.15.1/24 10.0.31.2/24
RouterE
192.168.15.1
RouterF
192.168.16.1
Figure 16-2. MSDP network topology
consult inet.2 as an alternative unicast routing table to use to base their RPF decisions
on. (This network is not congruent because the RouterG–RouterH link carries
only multicast traffic and the RouterB–RouterC link carries all unicast traffic.) The
RIBgroups populate inet.2 with unicast routes that are a subset of the unicast
routes in inet.0. The routes placed in inet.2 are only those unicast routes that
resolve to multicast-enabled routers. For PIM and MSDP to work, the inet.2 table
needs to include all the source’s prefixes, all the RP’s prefixes, and all direct routes.
The first RIBgroup you create, called mcast-rib, imports routes into and exports
routes from inet.2:
[edit routing-options]
aviva@RouterG# set rib-group mcast-rib export-rib inet.2
aviva@RouterG# set rib-group mcast-rib import-rib inet.2
When you associate this RIBgroup with MSDP and PIM, they consult it for their
RPF decisions.
The second RIB group, called if-rib, is for interface (direct) routes:
[edit routing-options]
aviva@RouterG# set rib-group if-rib import-rib [inet.0 inet.2]
This RIBgroup populates inet.2 with the router’s direct routes. Then associate the
if-rib RIB group with the router’s interfaces:
[edit routing-options]
aviva@RouterG# set interface-routes rib-group inet if-rib
610 | Chapter 16: IP Multicast
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