When designing OSPF networks; what is the purpose of using a hierarchical design? (Select all choices that apply)

When designing OSPF networks; what is the purpose of using a hierarchical design? (Select all choices that apply)

A. To reduce the complexity of router configuration
B. To speed up convergence
C. To confine network instability to single areas of the network
D. To reduce routing overhead
E. To lower costs by replacing routers
F. To decrease latency


Answer: B, C, D


Explanation:
An OSPF network designed in a hierarchical fashion with different areas is used because
a small change in the topology of a single area won't force every router to run the SPF
algorithm. Changes in one area are limited to that area only, not to every router within the
entire network. Confining the topology changes to one area reduces the overhead and
speeds the convergence of the network.