Enterasys Networks DFE-Gold Series Configuring OSPF

redistribute Configuring OSPF

Enterasys Matrix DFE-Gold Series Configuration Guide 21-19

Configuring OSPF

OSPFgracefulrestart,sometimesreferredtoasnon‐stopforwarding,providesforanOSPFrouter

toremainontheforwardingpathduringarestartofitsOSPFsoftware.Graceful‐restarthasfour

elementstoitsconfiguration:enabling,helperrouter,restartinterval,andstrictLSAchecking.

Enablinggracefulrestartinstructsthefirmwaretoperformagracefulrestart,ratherthana

standardOSPFrestart.Restartisonlyinitiatedbyafail‐over.GraceLSAsaresentwhenOSPFis

restartedonanothermodule.Whetherthefailoverisintentionalornot,thefailedrouterprotocol

isrestartedonanothermodule,anduponstartup,OSPFsendsgraceLSAsouttoitsneighbors

usingexistinglinkaggregationgroups.Usethegraceful‐restartenablecommandtoenablethe

gracefulrestartabilityonthisrouter.

Thehelperrelationshipwiththerestartingrouterisonapernetworksegmentbasis.Thehelper

monitorsthenetworkfortopologychanges.Ifnochangesoccur,thehelperroutercontinuesto

advertiseitsLSAsasthoughnorestartwasoccurring.Iftherestartingrouterwasthedesignated

router,thehelpercontinuestotreatitassuch.Ifatopologychangedoesoccur,gracefulrestartis

terminatedontherestartingrouterandastandardrestartoccurs.Helpermodecanbedisabledon

arestartingrouterneighborusingthegraceful‐restarthelper‐disabledcommand.Iftherestarting

routerreceivesanLSAindicatingadisabledhelper,thegracefulrestartterminatesandastandard

restartoccurs.

Arestartintervalprovidesforamaximumtimeinsecondsafterwhichthegracefulrestartwill

terminateshoulditnotcompleteorterminateforotherreasonswithintheinterval.Usethe

graceful‐restartrestart‐intervalcommandtochangetherestartintervalsetting.

StrictLSAcheckingassuresthatgracefulrestartwillterminateifthereisachangetoanLSAthat

wouldbefloodedtotherestartingrouter.StrictLSAcheckingcanbedisabled.Ifdisabled,a

changetoanLSAthatwouldbefloodedtotherestartingrouterwillnotcausethegracefulrestart

toterminate.Usethegraceful‐restartstrict‐lsa‐checking‐disabledcommandtodisablestrictLSA

checking.

ViewtherouterOSPFsectionoftheshowrunning‐configdisplaytoverifyanynon‐default

gracefulrestartsettings.

TheDFEsupportssinglerouterhighavailabilityfailoverusingthefollowingcomponents:

•OSPFgracefulrestart

•Non‐stoprouterframeforwardingoneachmodule

•Singlerouterconfiguration

•Routerprotocolprocessfailovertoanothermodule

•LinkAggregateGroup(LAG)connectivitytoneighboringrouters

TheDFEisadistributedroutingsystem.Theroutingprotocolprocessresidesonasinglerouter

module.Informationsuchasaccesslistrules,policyroutingrules,interfaceconfigurationandbest

routesarecalculatedbytheprotocolprocessanddistributedtoallmodules.Eachmodulehasits

Important Notice

OSPF is an advanced routing feature that must be enabled with a license key. If you have purchased an

advanced license key, and have enabled routing on the device, you must activate your license as described

back in “Activating Licensed Features” on page 2-58 in order to enable the OSPF command set. If you wish to

purchase an advanced routing license, contact Enterasys Networks Sales.