TABLE OF CONTENTS The explosive growth of networking and the Internet over the past decade has brought to light one of the few limitations of class-based, or classful, IP addressing. Under the current addressing scheme based on IPv4, Class A and B networks allow for a large number of hosts per network but fewer networks with unique network IDs, thus limiting the number of Class A and B networks in the world. Class C networks are more plentiful, but they are limited in the number of hosts allowed per network. As we learned in Chapter 1, there is always a trade off between the number of networks and the number of hosts you can have in the classful system.
In an effort to mitigate the looming shortage of unique public network addresses, two additional addressing schemes were devised:
The first method subnets a network to yield more network segments with fewer hosts per segment. The subnets are not equal divisions of the subnet, but can be of various sizes. This is known as variable length subnetting, which uses a Variable Length Subnet Mask (VLSM) to define subnets of different sizes based on the original network ID.
The second method combines unique network IDs into larger segments, essentially the reverse of subnetting, and is called supernetting.
In this chapter, we ll begin by reviewing how classful subnetting works and then we ll examine both variable length subnetting and supernetting. We ll also look at routing in Windows XP/Windows 2000 and routing in Windows...
