User manual

Table Of Contents
ZXR105900/5200SeriesUserManual(EthernetSwitchingVolume)
FIGURE19IGMPSNOOPINGAPPLICATION
MulticastGroupJoin
ThehostjoinscorrespondingmulticastgroupbysendinganIGMP
joiningmessage.WhentheswitchreceivestheIGMPhostreport
fromahostforaparticularmulticastgroup,theswitchaddsthe
portnumberofthehosttotheassociatedmulticasttableentry.
WhenotherhostsinthesameVLANareinterestedinthemulticast
trafcandsendamembershipreport,theswitchaddsthemtothe
existedforwardingentries.
Switchcreatesonlyoneforwardingentryforeachmulticastgroup
inthesameVLAN,forwardsthemulticasttrafcofthemulticast
groupinallportsreceivingthemembershipreport.
MulticastGroupLeave
HoststhatjoinedmulticastgroupmustrespondtoIGMPquery
messagetransmittedbyrouterperiodically.Aslongasonehost
respondstoIGMPqueryinaVLAN,theroutermustcontinuefor-
wardingtrafcofthemulticastgroupthatthehostjoinedtothe
VLAN.
Whenahostwantstoleaveamulticastgroup,itcouldignore
theIGMPquerymessagetransmittedbyrouterperiodically(called
“leavequietly”),orsendIGMPv2leavemessageofspecicgroup.
WhenIGMPSnoopinghearsIGMPv2leavemessageofspecic
group,theswitchsendsspecicgroupquerymessagetotheport
receivingthemessagetoquerywhetherotherhostsbelongingto
themulticastgroupareavailableinthisport.IfIGMPSnooping
cannotreceiveanyresponsemessageafterseveralqueries,itin-
dicatesthattherearenohostsbelongingtothemulticastgroup
68CondentialandProprietaryInformationofZTECORPORATION