Overview
A critical prerequisite to building a scalable network is having an efficient address architecture adhered to by all users of that network. Address architectures can take many different forms. Network addresses are always numeric, but they can be expressed in base 2 (binary), base 10 (decimal), or even base 16 (hexadecimal) number systems. They can be proprietary or open for all to see and implement. Address architectures can be highly scalable or intentionally designed to serve just small communities of users.

This chapter examines the address architecture implemented by the Internet Protocol (IP). As IP has evolved substantially over the past 20 years, so has its address architecture. This chapter describes the evolution of the IP address architecture and explains critical key components related to IP addressing, including subnetworks, subnetwork addresses or masks, classless interdomain routing (CIDR), variable-length subnet masking (VLSM) and route summarization

The content in this chapter is a prerequisite to understanding how to reduce routing table entries and the amount of route updates issued by routing protocols, such as OSPF (Open Shortest Path First). Knowing these IP addressing techniques enables you to define an appropriate IP address scheme for your network.