H3C Technologies H3C S12500 Series Switches - Manual (Page 97)

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Configuring IGMP
Overview
As a TCP/IP protocol responsible for IP multicast group member management, the Internet Group
Management Protocol (IGMP) is used by IP hosts and adjacent multicast routers to establish and maintain
their multicast group memberships.
The term "router" in this document refers to both routers and Layer 3 switches.
IGMP versions
• IGMPv1 (defined by RFC 1112)
• IGMPv2 (defined by RFC 2236)
• IGMPv3 (defined by RFC 3376)
All IGMP versions support the ASM model. In addition to the ASM model, IGMPv3 can directly
implement the SSM model. IGMPv1 and IGMPv2 must work with the IGMP SSM mapping function to
implement the SSM model.
For more information about the ASM and SSM models, see "Multicast overview."
Introduction to IGMPv1
IGMPv1 manages multicast group memberships mainly based on the query and response mechanism.
All multicast routers on the same subnet can get IGMP membership report messages (often called
"reports") from hosts, but the subnet needs only one router to act as the IGMP querier to send IGMP
query messages (often called "queries"). The querier election mechanism determines which router acts
as the IGMP querier on the subnet.
In IGMPv1, the DR elected by the working multicast routing protocol (such as PIM) serves as the IGMP
querier.
For more information about DR, see "Configuring PIM."