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PIM-SM, PIM-SSM, and PIM-BIDIR
PIM-SSM Operations
PIM in Source-Specific Multicast operation uses information found on source addresses for a multicast group
provided by receivers and performs source filtering on traffic.
• By default, PIM-SSM operates in the 232.0.0.0/8 multicast group range for IPv4 and ff3x::/32 (where
x is any valid scope) in IPv6. To configure these values, use the ssm range command.
• If SSM is deployed in a network already configured for PIM-SM, only the last-hop routers must be
upgraded with Cisco IOS XR Software that supports the SSM feature.
• No MSDP SA messages within the SSM range are accepted, generated, or forwarded.
PIM-Bidirectional Operations
PIM Bidirectional (BIDIR) has one shared tree from sources to RP and from RP to receivers. This is unlike
the PIM-SM, which is unidirectional by nature with multiple source trees - one per (S,G) or a shared tree from
receiver to RP and multiple SG trees from RP to sources.
Benefits of PIM BIDIR are as follows:
• As many sources for the same group use one and only state (*, G), only minimal states are required in
each router.
• No data triggered events.
• Rendezvous Point (RP) router not required. The RP address only needs to be a routable address and
need not exist on a physical device.
Restrictions for PIM-SM and PIM-SSM, and PIM BIDIR
Interoperability with SSM
PIM-SM operations within the SSM range of addresses change to PIM-SSM. In this mode, only PIM (S,G)
join and prune messages are generated by the router, and no (S,G) RP shared tree or (*,G) shared tree messages
are generated.
IGMP Version
To report multicast memberships to neighboring multicast routers, hosts use IGMP, and all routers on the
subnet must be configured with the same version of IGMP.
A router running Cisco IOS XR Software does not automatically detect Version 1 systems. You must use the
version command in router IGMP configuration submode to configure the IGMP version.
MLD Version
To report multicast memberships to neighboring multicast routers, routers use MLD, and all routers on the
subnet must be configured with the same version of MLD.
PIM-BIDIR Restrictions
• PIM SSM is not supported in the core for BIDIR traffic in the MVRF.
Cisco IOS XR Multicast Configuration Guide for the Cisco CRS Router, Release 5.2.x
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Implementing Multicast Routing on Cisco IOS XR Software
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