Enterasys Matrix DFE-Gold Series

Enterasys Matrix DFE-Gold Series Configuration Guide 9-1
9
IGMP Configuration
ThischapterdescribestheIGMPConfigurationsetofcommandsandhowtousethem.
About IP Multicast Group Management
TheInternetGroupManagementProtocol(IGMP)runsbetweenhostsandtheirimmediately
neighboringmulticastswitchdevice.Theprotocol’smechanismsallowahosttoinformitslocal
switchdevicethatitwantstoreceivetransmissionsaddressedtoaspecificmulticastgroup.
Amulticast‐enabledswitchdevicecanperiodicallyaskitshostsif
theywanttoreceivemulticast
traffic.IfthereismorethanoneswitchdeviceontheLANperformingIPmulticasting,oneof
thesedevicesiselected“querier”andassumestheresponsibilityofqueryingtheLANforgroup
members.
BasedonthegroupmembershipinformationlearnedfromIGMP,aswitchdevicecan
determine
which(ifany)multicasttrafficneedstobeforwardedtoeachofitsports.AtLayer‐3,multicast
switchdevicesusethisinformation,alongwithamulticastroutingprotocol,tosupportIP
multicastingacrosstheInternet.
IGMPprovidesthefinalstepinanIPmulticastpacketdeliveryservicesinceit
isonlyconcerned
withforwardingmulticasttrafficfromthelocalswitchdevicetogroupmembersonadirectly
attachedsubnetworkorLANsegment.
ThisswitchdevicesupportsIPmulticastgroupmanagementby
• passivelysnoopingontheIGMPqueryandIGMPreportpacketstransferredbetweenIP
multicastswitchesandIPmulticasthost
groupstolearnIPmulticastgroupmembers,and
•activelysendingIGMPquerymessagestosolicitIPmulticastgroupmembers.
ThepurposeofIPmulticastgroupmanagementistooptimizeaswitchednetwork’sperformance
somulticastpacketswillonlybeforwardedtothoseportscontainingmulticastgrouphostsor
multicastswitchdevicesinstead
offloodingtoallportsinthesubnet(VLAN).
InadditiontopassivelymonitoringIGMPqueryandreportmessages,theEnterasysMatrixSeries
devicecanalsoactivelysendIGMPquerymessagestolearnlocationsofmulticastswitchesand
memberhostsinmulticastgroupswithineachVLAN.
For information about... Refer to page...
About IP Multicast Group Management 9-1
IGMP Configuration Summary 9-2
Enabling / Disabling IGMP 9-2
Configuring IGMP 9-5