Internet Group Management Protocol (IGMP) is an essential feature of multicast messaging. IGMP instructs routers and switches to forward Ethernet multicast packets to only those device ports that have requested these packets.
In the absence of IGMP snooping, a switch forwards multicast packets out of all its ports, resulting in greater network traffic, wasted network bandwidth, and degraded network performance.
Configure one Ethernet network switch as the IGMP querier. This switch periodically polls the field devices connected to the network, which causes all connected devices to issue an IGMP Multicast Group Join message. The group message is received by all network switches, which update their multicast addressing information databases in response.
Similarly, when an Ethernet device transmits an IGMP Multicast Group Leave message, all network switches update their multicast addressing information databases by removing the device from their databases.
Multicast messaging reduces network traffic by:
Schneider Electric recommend the following:
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employ switches that support IGMP V2 or higher
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because IGMP snooping may be disabled by default, enable IGMP snooping for each network switch
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confirm that one switch is configured as the IGMP querier
