Intellinet 561099 - MultiCast

  8‐PortGigabitWeb‐SmartSwitch
19|Page
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3.3 MultiCast
3.3.1 IGMPSnooping
TheInternetGroupManagementProtocol(IGMP)letshostsandroutersshareinformationabout
multicastgroupmemberships.IGMPsnoopingisaswitchfeaturethatmonitorstheexchangeofIGMP
messagesandcopiesthemtotheCPUforfutureprocessing.TheoverallpurposeofIGMPSnoopingisto
limittheforwardingofmulticastframestoonlyportsthatareamemberofthemulticastgroup.
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AbouttheInternetGroupManagementProtocol(IGMP)Snooping
Computersandnetworkdevicesthatwanttoreceivemulticasttransmissionsneedtoinformnearby
routersthattheywillbecomemembersofamulticastgroup.TheInternetGroupManagementProtocol
(IGMP)isusedtocommunicatethisinformation.IGMPisalsousedtoperiodicallycheckthemulticast
groupformembersthatarenolongeractive.Inthecasewherethereismorethanonemulticastrouter
onasubnetwork,onerouteriselectedasthe‘queried’.Thisrouterthenkeepstrackofthemembership
ofthemulticastgroupsthathaveactivemembers.TheinformationreceivedfromIGMPisthenusedto
determineifmulticastpacketsshouldbeforwardedtoagivensubnetworkornot.Theroutercancheck,
usingIGMP,toseeifthereisatleastonememberofamulticastgrouponagivensubnetwork.Ifthereare
nomembersonasubnetwork,packetswillnotbeforwardedtothatsubnetwork.
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MulticastService
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YoucanenableordisableIGMPSnoopingonthisscreen.
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