OSPF Network Design Solutions, Second Edition

Stub Area Design

A stub area is a powerful network design technique. In OSPF, this area carries a default route and inter-area routes but does not carry external routes. Placing sections of the network in stub areas reduces network overhead because stub areas are essentially dead end areas. This reduces the routes being advertised across the network.

For example, consider that you were redistributing 10,000 routes into area 0 of your OSPF network. Standard areas receive all sent routes; however, stub area do not receive all sent routes. Instead, a default route 0.0.0.0/0 is advertised into the stub area, saving the routers inside from the entire added load. Therefore, stub areas allow for a reduction in LSA traffic and can make OSPF more stable. ...