Chapter 2. What You Need to Know About IPv6 Addressing

We’ll need to be familiar with the basics of IPv6 addressing as we learn and apply IPv6 address planning concepts and methods. If you already know this topic well, feel free to skip ahead to the next chapter.


Let’s review the basic representation of the IPv6 address. The IPv6 address is 128 bits long:

00100000 00000001 00001101 10111000 00000000 00010000 10101010 00100000
00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000001

Easy to write, easy to remember—that is, if you’re a computer[28] or a savant.

For everyone else, it’s easier to manage in its usual form, presented as 8 hextets[29] (each with up to 4 hexadecimal values) of 16 bits, separated by colons:



You’ll notice that we’re consistently using lowercase letters in our examples. IPv6 standards recommend lowercase letters when presenting addresses. But that’s just for human consumption: when formatting IPv6 addresses for internal storage in a database or application, uppercase, lowercase, or any combination of the two can be used. Also, various OSes and types of networking equipment may present (or allow for configuration of) an IPv6 address in either uppercase or lowercase with no impact on functionality. However, keep in mind that consistent address representation becomes important to find addresses in databases and spreadsheets more easily (especially if you don’t have, or can’t ...

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