Large-Scale IP Network Solutions (CCIE Professional Development)

The OSPF Area Concept

One of the most important concepts in OSPF is the existence of hierarchy and areas. OSPF allows collections of contiguous networks to be grouped together. Such a group, together with the routers maintaining interfaces to any of the included networks, is called an area. Each area runs a separate copy of the basic link-state routing algorithm.

Rather than treating the entire autonomous system as a single link-state domain, the topology of an area can be hidden. It is then invisible from the outside of the area. Similarly, routers in other areas know nothing of the topology outside their own area, which markedly reduces routing traffic.

Now that multiple areas are created in the network, there is no need for all the routers ...