Install Guide

Table Of Contents
Internet Group Management Protocol
(IGMP)
Internet group management protocol (IGMP) is a Layer 3 multicast protocol that hosts use to join or leave a multicast group.
Multicast is premised on identifying many hosts by a single destination IP address; hosts represented by the same IP address
are a multicast group. Multicast routing protocols (such as protocol-independent multicast [PIM]) use the information in IGMP
messages to discover which groups are active and to populate the multicast routing table.
IGMP Implementation Information
Dell EMC Networking Operating System (OS) supports IGMP versions 1, 2, and 3 based on RFCs 1112, 2236, and 3376,
respectively.
Dell EMC Networking OS does not support IGMP version 3 and versions 1 or 2 on the same subnet.
IGMP on Dell EMC Networking OS supports an unlimited number of groups.
Dell EMC Networking systems cannot serve as an IGMP host or an IGMP version 1 IGMP Querier.
Dell EMC Networking OS automatically enables IGMP on interfaces on which you enable a multicast routing protocol.
Topics:
IGMP Protocol Overview
Configure IGMP
Viewing IGMP Enabled Interfaces
Selecting an IGMP Version
Viewing IGMP Groups
Adjusting Timers
Enabling IGMP Immediate-Leave
IGMP Snooping
Fast Convergence after MSTP Topology Changes
Egress Interface Selection (EIS) for HTTP and IGMP Applications
Designating a Multicast Router Interface
IGMP Protocol Overview
IGMP has three versions. Version 3 obsoletes and is backwards-compatible with version 2; version 2 obsoletes version 1.
IGMP Version 2
IGMP version 2 improves on version 1 by specifying IGMP Leave messages, which allows hosts to notify routers that they no
longer care about traffic for a particular group.
Leave messages reduce the amount of time that the router takes to stop forwarding traffic for a group to a subnet (leave
latency) after the last host leaves the group. In version 1 hosts quietly leave groups, and the router waits for a query response
timer several times the value of the query interval to expire before it stops forwarding traffic.
To receive multicast traffic from a particular source, a host must join the multicast group to which the source is sending traffic.
A host that is a member of a group is called a receiver. A host may join many groups, and may join or leave any group at any
time. A host joins and leaves a multicast group by sending an IGMP message to its IGMP Querier. The querier is the router that
surveys a subnet for multicast receivers and processes survey responses to populate the multicast routing table.
IGMP messages are encapsulated in IP packets, as shown in the following illustration.
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