Enterasys Matrix DFE-Gold Series

Configuring OSPF redistribute
21-20 Routing Protocol Configuration
ownforwardingenginethatusesthisinformationtomakeforwardingdecisionslocallyonthe
modulethatreceivestheframe.Theseenginesindependentlymakeforwardingdecisionsbased
onrouteandruleinformationdistributedbytherouterprotocolprocess.Inastablenetwork,the
distributedrouteandruleinformationisfairlyconstant.If
therouterprotocolprocesswasto
suddenlyfail,forwardinginformationcurrentatthetimeofthe failureinallprobabilityisusable
fortheshorttimeafterthefailureuntilrecoveryoccurs.Duringthisrecoveryperiod,existing
connections(thatwerenotdirectlyusingthefailedmodule)remainineffect.New
connections
continuetobeinstalledusingthelastknownʺgoodʺforwardinginformation.Therouterprotocol
processthatfailedisdynamicallyrestartedonanothermodule.Theuserdoesnotconfigurewhere
therouterprocessisrunning.Therouterforwardingprocessremainsactiveoneverymodule.The
protocolprocessexchangesprotocolandmaintains
statethatitdistributestotheothermodules
anddoesnothavetorunonanyspecificmodule.Oneexceptiontothisruleisthatthemodule
musthave256Mofmemorytoberouterprotocolprocesseligible.
Uponfailureofamodulerunningtherouterprotocolprocess,theprotocol
processisstartedona
recoverymodule.OneofthefirstmessagesitsendstoitsOSPFneighborsisagraceLSA.High
availabilityfailoverwillsuccessfullyoccurifthefollowingistrue:
•Therouterisenabledforgracefulrestart
•Theneighborsareenabledtoparticipateasgracefulrest arthelper
•TheOSPF
deadintervalisconfiguredforasufficientperiodsuchthatthegraceLSAis
receivedbyitsneighborsbeforetheconfiguredOSPFdeadintervalexpires
•AndeachneighborisamemberofaLAGcommontothefailedrouter,allowingtheneighbor
toremainup
Figure 21-1 Physical and Logical Single Router HA Failover Configuration
Figure 21‐1depictsthephysical
andlogicalconfigurationsofthesinglerouterhighavailability
failovermechanism.Thebluelinesdisplaydirectneighborconnectionstotherouterenabledfor
OSPFgracefulrestartandmembersofLAGscommontothefailingrouter.Theredlinesdisplay
VLANconnectionscommontoboththefailingandrecoveryrouters.
Purpose
Toenableandconfigurethe OpenShortestPathFirst(OSPF)routingprotocol.
Rest of Routed
Network
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Neighbor B
Router
Neighbor A
Neighbor B
Router
OSPF
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LAG