# An Overview of IPv6 – CompTIA Network+ N10-006 – 1.8

April 1, 2015

IPv6 networking is becoming more popular, but the format of an IPv6 address is very different than our traditional IPv4 addressing. In this video, you’ll learn about the IPv6 address structure and how to compress an IPv6 address.

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IPv6 stands for Internet Protocol Version 6. It is a 128-bit address. This is a much larger address than our traditional IPv4 addresses. And one of the reasons we created IPv6 is so that we could have many, many more addresses available. You can see 340 undecillion addresses. That’s a lot of addresses.

If there are 6.8 billion people, they all could have this many addresses for each individual person. So based on that, you can see that IPv6 is designed to handle our addressing needs well into the future. If we were to take all 128-bits and draw it out, it looks something like this.

One thing that’s very different with IPv6 versus IPv4, is instead of expressing the addresses in decimal, we talk about IPv6 addresses in hexadecimal. So you’ll not only see the numbers zero through nine, you also see the letters a through f combined in that for a total number of 16 characters in hexadecimal. And you can see here is an IPv6 address, fe80::5d18:652:cffd:8f52.

It seems like a very complicated address. So let’s break it down a little bit and give you an understanding of exactly how an IPv6 address is structured. Although, it looks a little different, it is exactly the same as working with an IPv4 address. It’s just a much longer address, and it has a different way of expressing it in hexadecimal.

The double colons that we have here are signifying that there are zeroes in that spot. So we’re going to extend this out. And if we were to look at the uncompressed version of an IPv6 address, it’s actually this one– fe80, a bunch of zeroes. And then you can finally see the numbers added up there near the end of this. We’ll talk about IPv6 compression and how you can figure that out in just a moment.

If you finally do take those hexadecimal numbers and you write them out in binary, this is what it looks like. So you can see here are all 128 of those IPv6 bits all written out. We’ve separated out this address into 16-bit sections, and we’ve separated each of those sections with a colon. So you can see here’s 116-bit section. Here’s another. Here’s another.

You could also express this as a 2 bytes section. You may hear people refer to it as a 2 octets session. Total, we’ve got 16 full bytes that we can use in an IPv6 address for that total of 128 bits. As you can tell with IPv6, it’s a much bigger address, it has a different type of numbering system, and it’s a little bit more difficult to remember just the number or the IPv6 address of a device.

With IPv4 it was a lot easier. We could remember 192.168.1.1. That’s the IPv6 address of a server. This might be the IPv6 address of the same server. It’s not quite as straightforward. And because of that, we’re going to rely a lot more on our DNS. We can simply refer to those servers by name instead of having to remember the entire IPv6 address.

We don’t generally do a lot of subnetting in IPv6, because we have so many addresses available. There’s really no need to separate it down into smaller pieces to try to conserve address space like we did with IPv4. Because of that, you’ll generally see IPv6 addresses having a 64-bit subnet mask. You’ll see it written with a /64. That means the first 64 bits will be the network address and then you have all 64 bits after that to use as host addresses.

You’re probably not going to have a subnet that uses all of those bits just for hosts. But because you have so many addresses available, we don’t have to worry about that subnetting and we can keep it very simple by just separating it right in the middle and having 64 bits for the network and 64 bits for the host.

In our previous example, there was a double colon in the IPv6 address. That’s because that was a compressed IPv6 address. There were sections of zeroes and we replaced those sections of zeroes with simply a double colon so that the IPv6 address would be a little bit easier to read. If there are leading zeroes in a section of an address, you get rid of the leading zeroes as well to compress the address down even further. Let’s do an example of this.

We’ll start with an IPv6 address. Here it is the fe80. There’s a bunch of zeroes. Here some other numbers in the address. It;s a nice long address and we want to compress it. The first thing we’ll do is we’ll remove anything that has a leading zero. So we know there’s a leading zero here with the 00a7. There’s also one leading zero here with the 08d5.

So if we remove that, we’ve really got rid of all the leading zeroes in these three sections and the two leading zeroes here, and we got rid of this leading zero to make this a little bit easier to read. Now as you can see here, we do have a section where there is simply a 0 a 0 and a 0 altogether. We can simplify that even further by taking those groups, and it has to be two or more groups to really be useful here, and replacing that with a double colon. That means our number now simplifies to fe80.

There’s our double colon. We’re skipping all of those zeroes and then we’re bringing down the rest of what we have here. So that gives us a final IPv6 address of fe80::cabc:c800:a7:8d5. And although, that still is a very long address, it’s not something that you could easily remember. It is much easier to view certainly much easier than the fully listed IPv6 address that we have at the top.

One thing to keep in mind you can only replace this leading set of zeroes is grouping of zeroes with a double colon one time in an address. You can’t do that more than once or you won’t know exactly how many zeroes it’s replacing. So you would only be able to perform the double colon once. Even if there were other groups of zeroes later on in the address, you still would not be able to replace them. You have to choose one or the other and only have one set of double colons. Let’s perform another practice of a compression.

We’ll do exactly the same process we did in our last example. Here’s our nice long IPv6 address with the eight different sections. You can see even here there are a large number of zeroes and some leading zeroes on a number of these sections. We’re going to get rid of all the leading zeroes. So this simplifies it down quite a bit. But we do have this section right in the middle, where we have four zeroes in a row.

We can replace every single one of them with the double colon. So when we bring that down, you can see that it is simplifying this quite a bit. So we’ve gone through this very long address to the top. We’ve compressed it down and the final address is 2000:bb0::a0:2., a much simpler way talking about this very long address. And if you’re reading or writing or even viewing this in your operating system, you’ll see this compressed address used most often, instead of writing out this very long IPv6 address.

Category: CompTIA Network+ N10-006