R21xx-HP FlexFabric 11900 IP Multicast Configuration Guide

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Configuring IGMP
Overview
Internet Group Management Protocol (IGMP) establishes and maintains the multicast group
memberships between a Layer 3 multicast device and its directly connected hosts.
IGMP has three 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
ove
rview."
The term "interface" in the IGMP features collectively refers to Layer 3 interfaces, including VLAN
interfaces and Layer 3 Ethernet interfaces. You can set an Ethernet port as a Layer 3 interface by using
the port link-mode route command (see Layer 2—LAN Switching Configuration Guide).
IGMPv1 overview
IGMPv1 manages multicast group memberships based on the query and response mechanism.
All routers that run IGMP 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 designated router (DR) elected by the multicast routing protocol (such as PIM) serves as
the IGMP querier. For more information about DR, see "Configuring PIM."