Dell C1048P Port Extender Networking Configuration Guide for the C9000 Series - Page 621

area within the AS may not see the details of another area's topology. AS areas are known by their area number or the router's IP address. Figure 97. Autonomous System Areas Area Types The backbone of the network is Area 0. It is also called Area 0.0.0.0 and is the core of any AS. All other areas must connect to Area 0. Areas can be defined in such a way that the backbone is not contiguous. An OSPF backbone is responsible for distributing routing information between areas. It consists of all area border routers, networks not wholly contained in any area, and their attached routers. The backbone is the only area with a default area number. All other areas can have their Area ID assigned in the configuration. In the previous example, Routers A, B, C, G, H, and I are the Backbone. • A stub area (SA) does not receive external route information, except for the default route. These areas do receive information from inter-area (IA) routes. NOTE: Configure all routers within an assigned stub area as stubby, and not generate LSAs that do not apply. For example, a Type 5 LSA is intended for external areas and the Stubby area routers may not generate external LSAs. • A not-so-stubby area (NSSA) can import AS external route information and send it to the backbone. It cannot receive external AS information from the backbone or other areas. • Totally stubby areas are referred to as no summary areas in the Dell Networking OS. Open Shortest Path First (OSPFv2 and OSPFv3) 621