234 OSPF Commandsw w w . d e l l . c o m | s u p p o r t . d e l l . c o m User GuidelinesAuto-creation of OSPF areas is supported, so an OSPF area does not have to be definedbefore assigning it to an interface. To manually define an OSPF area, use the router ospf areacommand. If the auto-creation option is used, the area definition does not appear in therunning configuration file.If a question mark is specified at the end of the router ospf area command, the same hint isdisplayed twice at the prompt line.An OSPF routed network must contain an area 0. Only one sub-level of area hierarchy isallowed, that is all areas other than 0 must connect to area 0 via an ABR (area border router).An ABR is a router that is connected to two or more OSPF areas.Small networks usually will only have an area 0. Larger networks will have multiple OSPFareas to reduce the size of the IP route tables and to reduce the CPU and memory demandson the routers to a manageable level.It is not necessary to define an OSPF area globally. OSPF areas may also be defined with theinterface command.ExampleThe following example globally defines an OSPF area with the value of 1..router ospf redistribute ripThe router redistribute rip global configuration command enables incorporating IP routes thathave been learned via the RIP routing process into the OSPF routing process. To disable theredistribution of RIP routes, use the no form of this command.Syntaxrouter ospf redistribute ripno router ospf redistribute ripDefault ConfigurationThe redistribution of RIP routes is disabled.Command ModeGlobal Configuration modeConsole (config)# router ospf area 0.0.0.1
