Zte ZXR10 5900E Series - Page 149

Chapter5BGPConguration
àOptionaltransitiveattributes
àOptionalnontransitiveattributes
TheattributeWell-knownisidentiedbyallBGProuters.EachUPDATEmessage
hastocontaintheattributemandatory,buttheattributediscretionaryisoptional.
Foranoptionalattribute,itisnotsupportedbyallBGProuters.WhenBGPdoesnot
supportanattribute,ifitistransitive,itwillbeacceptedandsenttootherBGPpeers.
Ifthisattributeisnontransitive,itwilllbeignoredandnotsenttootherpeers.
RFC1771denesNo.1-7BGProuteattribute,asfollows:
àNo.1:ORIGIN
Routeorigin,thatistheASthatgeneratethisroutinginformation.
àNo.2:AS_PATH
ASpath,thatistheASgrouporserieswhichhasbeenpassedbyrouteentry.
àNo.3:NEXT-HOP
Thenexthopaddress.IBGPconnectionwillnotchangeNEXT-HOPsentby
EBGP .
àNo.4:MULTI_EXIT_DISC
ItisusedtodistinguishmanyexitstootherASs,whichisusedbylocalASrouter.
àNo.5:LOCAL-PREF
ItistransmittedwithinthelocalAS,indicatingthepriorityofeachpath.
àNo.6:ATOMIC_AGGREGATOR
àNo.7:AGGREGATOR
àNo.8:RFC1997denesanothercommonattribute:COMMUNITY
Here,No.1,2and3attributearewell-knownmandatoryattributes.No.5and6are
well-konwndiscretionaryattributes.No.7and8areoptionaltransitiveattributes.No.4
isoptionalnontransitiveattribute.Theyhavedifferentpriorities,LOCAL-PREFhasthe
highestpriority,andthesecondoneisAS-PATHandORIGIN.
ForotherattributesusedbyBGP ,pleaserefertoFRCdocumentation.
lFilteringRoutesbyRouteMap
ThebasesofperformingBGPareroutelterandattributeconguration.Bymeans
ofroutelter,theinputoroutputrouteattributescanbecontrolled.
Routemapisusedtocontrolroutinginformation,whichredistributesroutesbetween
routingareasbydeningrules.Theroutemapusuallycooperateswiththeroute
attributestodecideroute.
Tolterroutesbyroutemap,performthefollowingsteps.
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SJ-20150114102049-003|2015-01-15(R1.0)ZTEProprietaryandCondential