Enterasys Networks DFE-Gold Series Rest of Routed , Network 100.1.1.0/24, 100.1.1.0/24

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restart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
100.1.1.0/24
VLAN 100
100.1.1.5
100.1.1.3
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Neighbor A
Neighbor B
Router
Neighbor A
Neighbor B
Router
OSPF
100.1.1.0/24
VLAN 100
LAG