In addition to the backbone (area 0) and other non-backbone areas described and used in the examples in previous sections of this chapter, the OSPF specification also defines several 'special' types of areas. The configuration of these areas is primarily used to reduce the size of the Link State Database on routers residing within those areas by preventing the injection of different types of LSAs (primarily Type 5 LSAs) into certain Areas. These areas are:
- Not-so-stubby Areas
- Totally Not-so-stubby Areas
- Stub Areas
- Totally Stubby Areas