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This IP address looks like both the IPv4 address and the IPv6 address that's been assigned to that particular network node.

Hi, Leo. I see on my Norton Security map my IP address and right on top of that is also FE80::843: blah, blah, a bunch of other hexadecimal digits. I just want to make sure that this is normal and that should be listed on there. Thanks!

Absolutely.

What you're seeing are Internet protocol version 4 and version 6 addresses.

The IP addresses you're used to seeing are four numbers from 0 to 255 separated by periods. When you see it listed, it looks like 192.168.0.4 or similar.

So, you may wonder why doesn't the other IP address look like a normal IP address? Well, let me explain.

What is IPv6?

The problem with IPv4 addresses is that they are limited. It's a 32-bit number. That means there's a limit of four billion IP addresses on the planet.

But you know what? That's not enough. With the proliferation of Internet protocol or internet connected devices, the number of IP addresses actually required is much more than four billion.

Of course, there are a couple of ways around that, such as NAT routers. But really, we needed a new internet protocol. That's where Internet Protocol version 6 (IPv6) comes in.

How IPv6 works

IPv6 uses a 128-bit number as your IP address. Because of this, it uses a different kind of notation - a different way of displaying it.

You will see eight groups of four hexadecimal digits separated by colon. The hexadecimal digit is a digit 0 through 9 and A through F. In other words, there are 16 possible values. I'm sure you've seen various forms of this before. You can have eight groups of those, which gives you 128 bits worth of representation.

The other thing that's a little weird about IPv6 notation is that sometimes the groups can be empty. In your case, that's why you see FE80:: followed by the rest of the IPv6 address. The first group is FE80. The second group is blank. It's supposed to be. The program reading your IP address sees that it's blank and says, "Okay, part gets set to a default value." It makes IPv6 addresses shorter and easier to manage.

IPv6 on your machine

So, let's go back to what you're seeing in your Norton Security map. I believe you're seeing both the IPv4 address and the IPv6 address that's been assigned to that particular network node.

Yes, you can have both. Most recent versions of Windows have been released with both IPv4 and IPv6-enabled. Add an IPv6-enabled router or other form of IPv6 support, and you very well may see both IPv4 and IPv6 internet addresses in things like security reports and so on.

Article C6396 - April 12, 2013 « »

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Leo Leo A. Notenboom has been playing with computers since he was required to take a programming class in 1976. An 18 year career as a programmer at Microsoft soon followed. After "retiring" in 2001, Leo started Ask Leo! in 2003 as a place for answers to common computer and technical questions. More about Leo.

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3 Comments
dan
April 16, 2013 12:03 PM

Not trying to be anal (although I am being one), but 0-9 A-F is 16 possible values.

steven
April 16, 2013 4:24 PM

FIOS still fails to reach
http://test-ipv6.com/
and returns an error for the third year. I have IPv6 enabled and installed

Mark J
April 17, 2013 3:17 AM

@Dan
Thanks for catching that typo. It's fixed now.

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