5.1 Creating Multiple OSPF Areas
5.1.3 OSPF multi-area components
Hierarchical routing enables routing efficiency because it allows you to control the types of routing information that you allow in and out of an area. OSPF enables different types of routing updates by relying on areas and the routers connecting those areas.

The characteristics that areas and routers have will govern how they process routing information, including what types of LSUs each router can create, receive, and send. This subsection provides an overview of the following OSPF multi-area components (details about their usage and configuration appear in the following section):

  • Types of routers
  • Types of LSAs
  • Types of areas

Note The hierarchical topology possibilities of OSPF have three important advantages: reduced frequency of SPF calculations, smaller routing tables, and reduced LSU overhead.