The Un-Official CCNA guide #43: OSPF Areas

1. It is a good idea to divide a network into different OSPF areas.
2. Benefits of multiple OSPF Areas:

a. Each router maintains a smaller LSDB

b. OSPF algorithm takes up less processing power and is faster.

Important terms in OSPF

1. Backbone area: Backbone area, also known as area 0, is the area that all areas must be connected to.
2. Area Border Router (ABR) is the router that is connected to more than 1 areas.
3. Autonomous System Border Router (ASBR) is the router that is connected to more than 1 autonomous system/ routing domain.

Rules when implementing OSPF

1. All areas must be connected to the backbone area by at least 1 ABR.
2. All areas must be contiguous (Next to another area).