OSPF Overview
Matrix DFE Series and N-SA User’s Guide 8-5
thatfallwithinthespecifiedrangesarenotadvertisedintootherareasasinter‐arearoutes.
Instead,thespecifiedrangesareadvertisedassummarynetworkLSAs.
MatrixDFESeriesandN‐SAdevicesallowconfigurationofvariousOSPFareaparameters,
includingstubareas,defaultcost,authenticationmethod,andnot‐so‐stubbyareas(NSSAs).
InformationaboutrouteswhichareexternaltotheOSPFroutingdomainisnotsentintoastub
area.Instead,thereisadefaultexternal
routegeneratedbytheABRintothestubareafor
destinationsoutsidetheOSPFroutingdomain.
Stubcostspecifiesthecosttobeusedtoinjectadefaultrouteintoastubarea.Anauthentication
methodforOSPFpacketscanbespecifiedonaper‐areabasis.
Static Multipath Forwarding
TheMatrixDFE‐PlatinumSeriessystemsupportsOSPFandstaticmulti‐path.Ifmultiple,equal‐
costOSPForstaticrouteshavebeendefinedforanydestination,thentheDFESeriessystem
“discovers”andusesallofthem.Thesystemwillautomaticallylearnuptofourequal‐costOSPF
orstaticroutes
andretaintheminitsForwa rdingInformationBase(FIB).Theforwardingmodule
theninstallsflowsforthesedestinationsinaround‐robinfashion,orhash‐basedalgorithm.
Designating an OSPF Instance
OSPFisenabledbycreatinganOSPFinstance,whichisdesignatedbyanidentificationnumber
from1to65535.
Onceaninstanceiscreated,allthe router’s OSPFsettingsareconfiguredwithrespecttothe
instanceID.
Virtual Links
InOSPF,virtuallinkscanbeestablished:
•Toconnectanareaviaatransitareatothe backbone
•Tocreatearedundantbackboneconnectionthroughanotherarea
EachAreaBorderRoutermustbeconfiguredwiththesamevirtuallink.Notethatvirtuallinks
cannotbeconfiguredthroughastubarea.
Note: Although this does not apply to most changes to OSPF and other routing-based entries in
the configuration file, the following actions force the OSPF Link State Databases (LSDB) to re-
initialize:
• Adding a network to or removing one from an area.
• Changing an area’s type.
• Adding a summary range to or removing one from an Area Border Router.
Note: Only one OSPF instance is allowed per Matrix DFE Series routing module or N-SA device.
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