OSPF divides networks into areas to reduce complexity. Without areas, every router stores every link's state. In large networks, this overwhelms memory and CPU.
Area (Backbone): The core area. All other areas must connect to it.
Non-backbone areas: Connect to area through Area Border Routers.
Benefits of areas:
- Smaller routing tables
- Faster SPF calculations
- LSA flooding stays within areas
- Route summarization at area boundaries
A single-area design works for small networks. Once you exceed - routers, consider splitting into multiple areas.