OSPF area
also: OSPF domains, routing area
A logical subdivision of an OSPF network that reduces routing overhead by limiting the scope of link-state flooding. Areas are connected through a backbone area (Area 0) and communicate via Area Border Routers (ABRs).
OSPF (Open Shortest Path First) areas are hierarchical divisions of a routing domain designed to improve scalability and reduce computational load. Each area maintains its own topology database and performs independent shortest-path calculations, with only summary route information shared between areas.
The backbone area (Area 0) is mandatory and serves as the central hub; all other areas must connect to it either directly or through an Area Border Router (ABR). For example, in a large enterprise network, you might have Area 0 as the core, Area 1 for the finance department, Area 2 for engineering, and Area 3 for branch offices.
Areas reduce flooding of Link State Advertisements (LSAs), meaning routers only receive detailed topology changes for their own area plus aggregated routes from other areas. This significantly decreases memory usage and CPU overhead compared to a flat, single-area OSPF deployment.