IPv6 Network Administration

Chapter 1. The Unforeseen Limitations of IPv4

Those who cannot remember the past are condemned to repeat it.

George Santayana

So—if you were sitting down to design what was to become the most popular networking protocol in the world, what would you do?

Well, if you're anything like us, you probably still feel a chill on cold nights when you remember the more exciting times you've had debugging weird problems with IPv4. Consequently, we'd guess you'd try to create a protocol that, whatever other deficiencies it had, definitely didn't have the problems that kept you up until 3 a.m. last Saturday. The designers of IPv6 have done their best to address the well-known limitations of IPv4, while avoiding introducing new ways to keep you awake at night.

That's what this chapter is: an attempt to distill some of the more notable (some might say, broken) characteristics of IPv4, pointing out the motivations thereby deriving that drove the design of IPv6. Some of you might find this material familiar enough to skip; we don't mind. Others might find a refresher useful, or would like to know what tack we take on their favorite issue. For those and others, please read on.

Addressing Model

An IPv4 address is 32 bits long. They are usually written in dotted quad form, a.b.c.d where each of a, b, c and d are decimal numbers in the range 0-255. So the addresses range from 0.0.0.0 to 255.255.255.255. This means that there is an upper limit of 4,294,967,296, or about 4 billion, addresses. Since the address ...