OSPF Network Design Solutions, Second Edition

Backbone Area Design

The OSPF backbone (also known as area 0) is extremely important. If more than one area is configured in an OSPF network, one of these areas must be area 0. When designing networks, it is good practice to start with area 0 and then later expand into other areas. To summarize, the OSPF backbone is the part of the OSPF network that acts as the primary path for traffic that is destined to other areas or networks.

Accepted network design theory recommends a three-tiered approach (see Figure 4-24). This theory states that there should never be more than three tiers with a maximum of six router hops across the farthest points of the network. This type of design suits OSPF well because of its area concepts and need for hierarchical ...