DEMO: IPv6 Subnetting - Advanced

Using Subnetting to Create Logical Structure

One of the great things about IP version 6 is it gives us a lot of freedom, a lot of ways we can do subnetting. Let's take a look at a more advanced way of using subnetting to create logical structures within our network.

We could have a company that has multiple sites and multiple locations. An example of a network I worked on in the past is I had a whole campus area network, and so we sectioned things off into zones and we had student networks and staff networks, and we really got granular with that.

So what does that look like? Let's say you have three regions, and at each of those regions — one region has four sites, another has three sites, maybe one has two sites — and then within there you have three departments, or maybe it's 10 departments, or something to that effect.

What you can do, because you have such a wide range to work with and you've got the ability to make 65,000 different networks — if you were to calculate this out, if you had three regions and you had a few sites per each region and you had a few departments, then you'd have quite a few networks, but it's still nothing compared to 65,000. So what we can actually do is assign a nibble to each one of these.

Maybe the first one is going to be just the region. Since this is four bits, we have up to 16 regions here, so our three is well covered in there. And then we have nine sites, so let's say the second one is going to be the sites — so this is for sites here, and we have 16 different sites that we can have per region. And then we have three departments, so anything left over we could just say this is for the departments, and we've got 256 departments that we could have.

Or let's say I determine that I want more sites per region — then maybe I could cut this over and split it up a little differently. So I've got some ways to organize this, but the key to this is you do it by nibble, and it makes life so much easier when you're doing the subnetting. It really makes it real easy to break this out.

Assigning the Addresses

So then I can start breaking this down into what are the IP addresses I'm actually assigning. Here at the top I've got what is assigned to me, which is a /48 here. And then what I do is I say, okay, well that first nibble is going to represent the region, so I've got zero for US West, I've got a one for US East, I've got a two for Mexico. You'll notice then that trickles down to all sites in that region — so 0 0000 z0 Z for everything in US West; here's one, one, one, one, one for everything in US East; we've got 2, two, two. You get the point, that it's the same throughout this.

And then I break it down even further: okay, what are the sites? For Seattle it's going to be zero, for Portland it's going to be one, for San Francisco it's going to be two, and for Los Angeles it's going to be three. So if we take a look at Los Angeles, it's broken down into multiple departments here, each one of them: zero for management, one for operations, two for sales. And that's going to be seen the same no matter what site you're in.

So now I know just by looking at a number: if I see a one in the region area, I know it's US East. If I see, let's say, a 21, I'm going to know that that's Tijuana, that's in Mexico and it's the Tijuana site. If I see a 2000, or let's say a 0302, then I know zero is going to be US West, I know three means it's Los Angeles, and 02 means that it's the sales network.

So I can easily identify any of the networks. I can do things like ACLs where I can start blocking traffic and making things more secure — this makes it really easy to do that type of work, and it makes it really easy to identify certain traffic and where it's going. So it really just works out really well when you have so many bits that you can work with, and you can quickly identify where all of this traffic is coming from and how to assign the traffic out to begin with.