Single-area OSPF is useful in smaller networks where the web of router links is not complex, and paths to individual destinations are easily deduced.

However, if an area becomes too big, the following issues must be addressed (see the figure for illustration):

To make OSPF more efficient and scalable, OSPF supports hierarchical routing using areas. An OSPF area is a group of routers that share the same link-state information in their link-state databases.