Join Mike Meyers for an in-depth discussion in this video Introduction to IPv6 addressing, part of CompTIA Network+ (N10-006) Cert Prep: 5 Advanced IP Networking.
- This is an IP address. Now hopefully you could recognize this an IP address. We're gonna have four groups which we'll call octets that are numbered from zero to 255, and they're separated by three periods. And this type of addressing structure which is actually a 32-bit addressing structure has been around since well arguably the late 70s, early 1980s, and it's done a great job as a 32-bit addressing scheme. We, in theory at least, have four billion IP addresses, but it has one problem and that is we've run out of IP addresses.
I mean there are pretty much almost none left. So if new devices want to join the Internet, we're gonna have to come up with a new numbering system. Luckily for us, the new numbering system's been in the works, well, since for about 10 years now and this numbering system is known as IPv6. Oh, and by the way, this old school address, this is what we now call IPv4. So let me show you your first IPv6 address. Whoa! All right, this is a pretty long address. Takes up pretty much the whole screen and that's good because it's actually a 128-bit address.
This address has an address space as we say of something, in fact the number is so big, that I don't even know how to describe the number to you. It would be like all the air molecules on Earth times about seven. So this is a huge number of IP addresses and hopefully it'll last for a while. Now if you look at this big long address, one of the things you need to appreciate is that, well, it's really a big hassle to write out IPv6 addresses. So the important thing to appreciate right now is that we do a lot of abbreviation when it comes to IPv6 addresses.
So let's take this big long address and start abbreviating it. Now the first thing I'm gonna do here is I'm gonna drop all the leading zeros. So where it says 00c9, we just say c9. Or where it says 04d7, we just say 4d7. So that reduces things tremendously. Oop, getting a little shorter already. The next thing we can do is anywhere you have a group of four zeros, you just replace it with a single zero. So I've got what, one, two, three of these? Let's replace those with a single zero.
Yup, it's getting smaller all the time. Now you'll notice that we still have eight groups and that's important because when we talk about IPv6 addresses it's always gonna be eight groups separated by seven colons. Now keep in mind that these addresses are hexadecimal so that's why we have letters in there as well as numbers. Okay, now we're not quite done yet. There's one more thing for us to do and that's for us to go in and actually get rid of the long strings of zeros. So, for example, here where we have two groups of all zeros, we can replace that with simply a double colon.
Now that's great, but you need to be very, very careful about this 'cause people will see this and you might want to do something like this. Here where we have that one group of zeros by itself, we can't replace that with a double colon. All right, so no we can't do that. No double colons in more than one place. So let's go ahead and put that one back. There we go. The double colons replace long strings of zeros. So it works out perfectly well, but do keep in mind we can only do this in one place.
So while we're in here, let me show you a really, really cool IPv6 address. You ready? Yup, that's all zeros with just a one on the end. This is your loopback address. This is the equivalent of 127.0.0.1 in IPv4. So let's go ahead and take advantage of our abbreviation skills and let's see how small we can make this. So we can take all groups of four zeros and replace them with a single zero. Good. We can dump the leading zeros off that last grouping so 0001 becomes just 1 and now we can replace any single string of zeros with a double colon.
You're right. We can delete all of this and make it a double colon. So your loopback address in IPv6 is nothing more than good old ::1. On the Network+ exam there's a good chance you're gonna be stumbling into IPv6 addresses and it's going to expect you to be able to both compress them and bring them out to their full size if necessary. They're gonna be looking for legitimate IPv6 addresses. So watch out for silly tricks like only having seven groups instead of eight, or having too many characters between the colons, little basic stuff like that.
IPv6 is great and it's here, and it's really long addresses, and it's good for us to be able to abbreviate.
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