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