| A scalable network requires an
addressing scheme that allows for growth. As you add new nodes and
new networks to the enterprise, existing addresses may need to be
reassigned, bloated routing tables may bog down routers, and the
supply of available addresses may simply run out. You can avoid
these unpleasant consequences with careful planning and deployment
of a scalable network-addressing system.
Although network designers can choose
among many different network protocols and addressing schemes, the
emergence of the Internet and its nonproprietary protocol, TCP/IP,
has meant that virtually every enterprise must implement an IP
addressing scheme. In fact, as companies such as Apple and Novell
have recently migrated their network software to TCP/IP (and away
from their proprietary protocols), many organizations opt to run
TCP/IP as the only routed protocol on the network. The bottom line
is that today's 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. 20 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 could survive the Internet's exponential growth. Meanwhile, an
even more extendible 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 Internet's dominant protocol.
This chapter 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),
and route summarization. Finally, this chapter examines advanced IP
implementation techniques, such as IP unnumbered, Dynamic Host
Configuration Protocol (DHCP), and helper addresses.
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