Chapter 3. IP Addressing and Allocation Techniques

This chapter covers the following key topics:

• Overview of Internet addressing— Provides an overview of IPv4 Class A/B/C addressing and basic subnetting concepts.

• Variable-length subnet masks (VLSMs)— Provides a description of variable-length subnet masks and how they can be used in efficient assignment of the IP address space.

• IP address space depletion— Discusses how the problem of IP address space depletion is being managed through creative address allocation, supernetting, private addressing, and next-generation protocols.

• Private addressing and Network Address Translation (NAT)— Discusses how NAT software is used to map between private and global IP addresses.

• IP version 6 (IPv6)— Provides an overview of the IP next generation (IPng) addressing scheme and how it maps to the hierarchical model offered by CIDR and IPv4.

This chapter begins with a brief history of Internet addressing, providing information on traditional IP version 4 (IPv4) addressing and subnetting models. From there, you'll learn about some of the issues surrounding address space depletion on the Internet. Then we'll examine IP addressing techniques and allocation strategies such as variable-length subnet masking (VLSM), classless interdomain routing (CIDR), and Network Address Translation (NAT). The chapter finishes with a brief introduction to IP version 6 (IPv6).

Addressing strategies are of direct and fundamental relevance to routing architecture in any network. One of the basic functions of routing architecture and routers is to accommodate addresses for all the traffic they direct. With the explosive growth of the Internet, the sheer number of addresses and the evolution of new addressing strategies have presented new challenges for routing architectures. An understanding of the history and fundamentals of IP addressing will no doubt play a key role in your ability to quickly grasp routing protocol concepts.