Zte ZXR10 5900E Series - Page 18

ZXR105900ESeriesCongurationGuide(IPv4Routing)
RIPprovidesthefollowingfourtypesoftimers:
àUpdatetimer
SwitchrunningRIPtransmitsrouteupdatemessageatacertaininterval(30sby
default),whichreectsalltheroutinginformationoftheswitch.Thisprocessis
calledroutinginformationadvertisement.
àInvalidtimer
Invalidtimer:Whenaswitchfailstoreceiveupdateinformationfromanother
switchinacertaintimeperiod(180sbydefault),itmarkstheroutesprovidedby
theswitchtobe"unavailable".
àHolddowntimer
Afterlearningthatroutesareunavailable,theswitchwillenterhold-downstate.
Ifswitchreceivesrouteupdatepacketwithinthedefault180secondsorifswitch
failstoreceiverouteupdatepacketafter180seconds,theholddowntimerwill
stoptiming.
àFlushTimer
Whenitisnotupdatedinthesucceedingperiodoftime(240sbydefault),the
switchclearstheroutecompletelyfromtheroutingtable.
lRIPRouteUpdate
RIPprotocolemploystriggerupdatetospeedupthespreadofroutingchangesinthe
RIProutingdomain.WhenaRIProuterdetectsthataninterfaceisworkingorhas
stoppedworking,aneighbornodeisdownoranewsubnetorneighbornodejoins
in,itwilltransmitatriggerupdate.Thetriggerupdatepacketonlycontainschanged
route.
RIPprotocolusespoisonreversetospeedupprotocolconvergence.Thepoison
reversesetsthemetricoftheunreachablenetworkprexestobe16(meaning
unreachable).Afterreceivingrouteupdatepacketofthemetric,theswitchwill
discardtherouteinsteadofwaitingfortheagingtime.
RIPusessplithorizontopreventloopandreducethesizeofrouteupdatepacket.Split
horizonmeansthatifaninterfacereceivesarouteupdatepacket,itwillnottransmit
thisupdatepacketfromitselftoothers.
RIPWorkingPrinciple
RIPdenestwokindsofmessagetypes,requestandresponsemessages.Request
messageisusedtosendaupdatetoneighborswitch,andresponsemessageisused
totransmitrouteupdate.
1.Atthestart,RIPbroadcastsormulticastpacketswhichcontainrequestmessagefrom
everyRIPinterface.
2.Later,RIPentersaloopstate,italwaysmonitorstheRIPrequestorresponse
messagesfromotherswitches,andtheneighborswitcheswhichaccepttherequest
willreplyresponsemessagescontainingtheirroutingtables.
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SJ-20150114102049-003|2015-01-15(R1.0)ZTEProprietaryandCondential