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SecureStack C2 Configuration Guide 13-1

IGMP Configuration

ThischapterdescribestheIGMPConfigurationsetofcommandsandhowtousethem.

IGMP Overview

About IP Multicast Group Management

TheInternetGroupManagementProtocol(IGMP)runsbetweenhostsandtheirimmediately

neighboringmulticastdevice.Theprotocol’smechanismsallowahosttoinformitslocaldevice

thatitwantstoreceivetransmissionsaddressedtoaspecificmulticastgroup.

Amulticast‐enableddevicecanperiodicallyaskitshostsiftheywantto

receivemulticasttraffic.If

thereismorethanone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devicecandeterminewhich(if

any)multicast

trafficneedstobeforwardedtoeachofitsports.AtLayer‐3,multicastdevicesuse

thisinformation,alongwithamulticastroutingprotocol,tosupportIPmulticastingacrossanIP

network.

IGMPprovidesthefinalstepinanIPmulticastpacketdeliveryservice,sinceitisonlyconcerned

withforwarding

multicasttrafficfromthelocaldevicetogroupmembersonadirectlyattached

subnetworkorLANsegment.

ThisdevicesupportsIPmulticastgroupmanagementbypassivelysnoopingontheIGMPquery

andIGMPreportpacketstransferredbetweenIPmulticastdevicesandIPmulticasthostgroupsto

learnIPmulticastgrou p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devicesinsteadoffloodingtoallportsinthesubnet(VLAN).

InadditiontopassivelymonitoringIGMPqueryandreportmessages,the

SecureStackC2canalso

activelysendL3IGMPquerymessagestolearnlocationsofmulticastdevicesandmemberhosts

inmulticastgroupswithineachVLAN.

However,notethatIGMPneitheraltersnorroutesanyIPmulticastpackets.SinceIGMPisnot

concernedwiththedeliveryofIPmulticastpacketsacrosssubnetworks,

multicastroutingis

neededifIPmulticastpacketshavetoberouted acrossdifferentsubnetworks.

For information about... Refer to page...

IGMP Overview 13-1

Configuring IGMP at Layer 2 13-2

Configuring IGMP on Routing Interfaces 13-10

Enterasys SecureStack C2 C2G170-24 User Manual

Other manuals for Enterasys SecureStack C2 C2G170-24