Content

| Overview

A scalable network requires an addressing scheme that allows for growth. However, several unanticipated consequences can result from unmanaged network growth. As new nodes and new networks are added to the enterprise, existing addresses may need to be reassigned. Excessively large routing tables may slow down older routers, and the supply of available addresses may simply run out. These unpleasant consequences can be avoided with careful planning and deployment of a scalable network addressing system.

Network designers can choose among many different network protocols and addressing schemes. However, with the emergence of the Internet and its nonproprietary protocol, TCP/IP, this has meant that virtually every enterprise must implement an IP addressing scheme. In addition to TCP/IP, there have been several proprietary network protocols and addressing schemes used. Companies such as Apple and Novell have recently migrated their network software to TCP/IP and away from their proprietary protocols. Presently, many organizations choose to run TCP/IP as the only routed protocol on the network. The bottom line is that administrators must find ways to scale their networks by using IP addressing.

Unfortunately, the architects of TCP/IP could not have predicted that their protocol would eventually sustain a global network of information, commerce, and entertainment. Twenty years ago, IP version 4, (IPv4) offered an addressing strategy that, although scalable for a time, resulted in an inefficient allocation of addresses. Over the past two decades, engineers have successfully modified IPv4 so that it can survive the exponential growth of the Internet. Meanwhile, an even more extensible and scalable version of IP, IP version 6 (IPv6), has been defined and developed. Today IPv6 is slowly being implemented in select networks. Eventually, IPv6 may replace IPv4 as the dominant Internet protocol.

This module explores the evolution and extension of IPv4, including the key scalability features that engineers have added to it over the years:

- Subnetting
- Classless interdomain routing (CIDR)
- Variable length subnet masking (VLSM)
- Route summarization

Finally, this module examines advanced IP implementation techniques such as the following:

- IP unnumbered
- Dynamic Host Configuration Protocol (DHCP)
- Helper addresses