4-13To do... Use the command... RemarksEnter system view system-view —Configure the router ID router id router-idOptionalIf multiple OSPF processes run on arouter, you are recommended to usethe router-id keyword in the ospfcommand to specify different routerIDs for different processes.Enable OSPF and enterOSPF viewospf [ process-id[ router-id router-id ] ]RequiredEnter OSPF view.Enter OSPF area view area area-id —Configure the networksegments in the areanetwork ip-addresswildcard-maskRequiredBy default, an interface does notbelong to any area.z In router ID selection, the priorities of the router IDs configured with the ospf [ process-id[ router-id router-id ] ] command, the router id command, and the priorities of the router IDsautomatically selected are in a descending order.z Router IDs can be re-selected. A re-selected router ID takes effect only after the OSPF process isrestarted.z The ospf [ process-id [ router-id router-id ] ] command is recommended for configuring router IDsmanually.z An OSPF process ID on a router must be unique.z One segment can belong to only one area and you must specify each OSPF interface to belong toa particular area.OSPF Area Attribute ConfigurationArea partition in OSPF reduces the number of LSAs in the network and enhances OSPF scalability. Tofurther reduce routing table size and the number of LSAs in some non-backbone areas on the edge ofthe AS, you can configure these areas as stub areas.A stub area cannot redistribute any external route. For this reason the concept of NSSA is introduced.Type7 LSAs can be advertised in an NSSA. Type7 LSAs are generated by ASBRs in the NSSA, and willbe transformed into Type-5 LSAs (AS-external LSAs) whey reaching ABRs in the NSSA area, which willthen be advertised to other areas.After area partition, the OSPF route updates between non-backbone areas are exchanged by way ofthe backbone area. Therefore, OSPF requires that all the non-backbone areas should keep connectivitywith the backbone area and the backbone area must keep connectivity in itself.If the physical connectivity cannot be ensured due to various restrictions, you can configure OSPFvirtual links to satisfy this requirement.
