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41-3
Cisco ASR 901 Series Aggregation Services Router Software Configuration Guide
OL-23826-09
Chapter 41 IPv4 Multicast
Feature Overview
Supported Protocols
• Basic multicast routing
• IGMP
• PIMv4 SSM
• PIMv4 SSM Mapping
• PIM MIB
• PIM Sparse mode
• Static Rendezvous Point (RP)
• Auto RP
• Bootstrap router (BSR)
PIM SSM for IPv4
PIM SSM is the routing protocol that supports the implementation of SSM and is derived from the PIM
sparse mode (PIM-SM). IGMP is the Internet Engineering Task Force (IETF) standards track protocol
used for hosts to signal multicast group membership to routers. IGMPv3 supports source filtering, which
is required for SSM. In order for SSM to run with IGMPv3, SSM must be supported in the device (the
host where the application is running) and in the application itself.
Source Specific Multicast
SSM is a datagram delivery model that best supports one-to-many applications, also known as broadcast
applications. SSM is a core networking technology for the Cisco implementation of IP multicast
solutions targeted for audio and video broadcast application environments and is described in RFC 3569.
The following two components together support SSM:
• PIM SSM
• IGMPv3
Protocol Independent Multicast
The PIM protocol maintains the current IP multicast service mode of receiver-initiated membership. PIM
is not dependent on a specific unicast routing protocol; it is IP routing protocol independent, and can
leverage whichever unicast routing protocols are used to populate the unicast routing table, including
Open Shortest Path First (OSPF), Border Gateway Protocol (BGP), Intermediate System-to-Intermediate
System (IS-IS), and static routes. PIM uses unicast routing information to perform the multicast
forwarding function.
Although PIM is called a multicast routing protocol, it actually uses the unicast routing table to perform
the RPF check function instead of building up a completely independent multicast routing table. Unlike
other routing protocols, PIM does not send and receive routing updates between routers.
For more information on SSM and PIM, see the IP Multicast Technology Overview document at:
http://www.cisco.com/en/US/docs/ios-xml/ios/ipmulti_pim/configuration/xe-3s/imc_tech_oview.html