Dell Force10 S50-01-GE-48T FTOS 8.4.2.7 Configuration Guide for E-Series TeraS - Page 693

Figure 32-1. Autonomous System Areas Router M Router E Router F Router K Router L Area 100 Router D Router C Router B Area 0 Router A Area 200 Router G Router H Router I Router J Area 300 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 Autonomous System (AS). All other areas must connect to Area 0. Areas can be defined in such a way that the backbone is not contiguous. In this case, backbone connectivity must be restored through virtual links. Virtual links are configured between any backbone routers that share a link to a non-backbone area and function as if they were direct links. 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 an default area number. All other areas can have their Area ID assigned in the configuration. Figure 32-1 shows Routers A, B, C, G, H, and I are the Backbone. Open Shortest Path First (OSPFv2 and OSPFv3) | 693