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.