R3303-HP HSR6800 Routers IP Multicast Configuration Guide

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With the IGMP SSM mapping feature configured, when Router A receives an IGMPv1 or IGMPv2 report,
it checks the multicast group address G carried in the message and does the following:
• If G is not in the SSM group range, Router A provides the ASM service.
• If G is in the SSM group range but no IGMP SSM mappings that correspond to the multicast group
G have been configured on Router A, Router A drops the message.
• If G is in the SSM group range and the IGMP SSM mappings have been configured on Router A for
multicast group G, Router A translates the (*, G) information in the IGMP report into (G, INCLUDE,
(S1, S2...)) information based on the configured IGMP SSM mappings and provides SSM service.
NOTE:
The IGMP SSM mapping feature does not process IGMPv3 reports.
For more information about the SSM group range, see "Configuring PIM."
IGMP proxying
In some simple tree-shaped topologies, it is not necessary to configure complex multicast routing
protocols, such as PIM, on the boundary devices. Instead, you can configure IGMP proxying on these
devices. With IGMP proxying configured, the device serves as a proxy for the downstream hosts to send
IGMP messages, maintain group memberships, and implement multicast forwarding based on the
memberships. In this case, the IGMP proxy device is a host but no longer a PIM neighbor to the upstream
device.
Figure 28 IGMP proxying
As shown in Figure 28, an IGMP proxy device has the following types of interfaces:
• Upstream interface—Also called the "proxy interface". A proxy interface is an interface on which
IGMP proxying is configured. It is in the direction toward the root of the multicast forwarding tree.
An upstream interface acts as a host that is running IGMP. Therefore, it is also called the "host
interface".