Cisco CCNA 200-301 – IPv6 Addressing and Routing Part 3

5. IPv6 Global Unicast Addresses Lab Demo

In this lecture, you’ll learn how to configure IPV Six Global Unicast addresses with a lab demo. Just before I get into that, there’s another thing I want to tell you about, which is about broadcast and multicast in IPV Six. In IPV four, we can broadcast to all hosts using the at 255-25-5255 destination address routers. Don’t forward broadcast traffic by default, so that traffic will hit everything in the local subnet, but it won’t go beyond there. IPV Six does not support broadcast traffic at all. It does, however, support multicast to all hosts on the local subnet using the destination address FF Two double call on one.

So that is functionally equivalent to the broadcast. In IPV four, many services which do use that 255-25-2525 broadcast address in IPV Four use a more specific multicast address in IPV six. For example, if a host sends out a DHCP request, if that’s in IPV Four, it gets broadcast so it hits all hosts and they all have to process it. In IPV six, it gets sent to FF Five double colon One Three, which is the DHCP server multicast address. So it’s only the DHCP servers that are listening for it that will process that traffic. So it makes your broadcast equivalent and your multicast traffic more efficient in IPV six. Okay. Onto our actual global unicast address configuration.

So first thing that we need to do is enable IPV Six unicast routing on your iOS routers. IPV Four routing is enabled by default, but IPV Six is not. So you have to turn it on. The way you do that is a global config. Enter the command IPV six unicast routing. You’re then ready to configure the IPV Six addresses on your interfaces. In IPV Four, you would go to the interface and then enter the command IP address and then the IP address.

For IPV Six, almost all the commands are the same as they are in IPV Four, but rather than saying IP, we say IPV Six. So it configure an address on an interface. We go to the interface first. In the example here, I’ve gone to Interface Fast Zero, and then the command is IPV Six Address, and then the address that you want to enter to verify the IPV Six addresses on your router.

Again, in IPV Four, we would say show IP Interface Brief. So check IPV Six addresses. It’s a show. IPV Six interface brief. Okay? So let’s actually configure this in the lab. So I’ll do it using the topology. You can see on the slide here. Let’s go to put a and I will configure r one I’ll just leave it in the top right window here so you can see the topology as well. Because those IPV Six addresses do get pretty long, it’s pretty hard to remember them. So on R four, I’ll go to global configuration, enter IPV six unicast routing, and I’ll configure interface fast 20 first.

It’s going to have IPV Six address 2001 colon DB eight. Notice I’m entering it in lower case here. The IPV six address is not case sensitive, so it doesn’t matter whether it’s in capitals or lowercase. Then zero colon zero double colon one and 64 is my IPB six address on fast 20. So that’s how you configure it. You enter the address and then slash and then the subnet mask all in one command. That’s the correct syntax. And this is on a router. So also remember to do a no shutdown on the interface. On our switches, interfaces are up by default, but on routers we’re administratively shut down by default. So you need to remember to do a no shutdown to bring the interface up. I’ll also configure interface fast Zero and that is IPV six address 2001 DB eight, colon zero 64 and a no shutdown. And to verify it, show IPV six interface brief. And I can see there is the IPV six address that I configured on fast zero zero and the address that I configured on Fast 20. You notice that there’s also these addresses beginning with feat as well. Those are link local addresses.

Don’t worry about them yet, we’ll cover those in another lecture later in this section. Let’s also put an IPV six address on R Two as well. So I’ll go there and go to Global Configuration, IPV six unicast routing and then on interface fast Zero, IPV six address. And what I’ll do is I’ll put it in the full form of the address here. I won’t shorten it at all. So I’ll say IPB six address 2001 DB eight colon zero 64. So when you enter the address in the router, you can put in the shortened version or you can put in the long version. They both mean the same thing and the router doesn’t mind. It will take either way. I do a no shut down on here and now.

Notice if I do a show IPV six interface brief, the router is going to automatically shorten that to the short version of the address for me. Okay? So that’s how we configure our IPV six addresses on the router. Once you’ve done that, the way they work is really the same as it is with IPV four. So all the routing and switching is basically the same. But if we want to check connectivity, it’s the same way that we do it with IPV four. So IPV four, I would use a ping. I can use a ping in IPV six as well. So from R two, I will ping over to R one at 2001 DB 80 one double cool on one and you see that the ping succeeds. I could also use a trace route the exactly the same way that I do with IPV four as well. Okay, so that was a basic configuration to get IPV six addresses on our routers. See in the next lecture where we’re going to get deeper into IPV six.

6. EUI-64 Addresses

In this lecture, you’ll learn about Eui 64 addresses. Rather than manually configuring the full IPV six address on a router’s interface, it can generate the full IPV six address for itself. If you enter the interface that you want to do this on and the 64 network prefix that is to be used, the host portion of the address will then be derived from the interfaces Mac address. And the Mac address is always guaranteed to be globally unique. But a Mac address is 48 bits long and the host portion of an IPV six address is 64 bits long. So to derive the host portion of the IPV six address from the Mac address, we need to make the Mac address longer. We need to extend it from 48 bits to 64 bits. The way that that is done is FF colon fe is injected into the middle of it. Also, the 7th bit is inverted. So looking at an example with our network here, let’s say that we haven’t configured any IPV six addresses anywhere. And for an example, we’re going to use Eui 64 addresses on R one.

So on R one we’re going to go on to the fast zero interface and say that the network prefix there is 2001 colon, DB eight, colon zero one, double colon 64 and tell the router to generate an Eui 64 address. It will then automatically generate an address for itself on that interface with the correct network portion of the address. And in the second half of the address, the host portion will be derived from the Mac address. So in the example here, we’re not going to use one at the end. We’re going to just have it automatically generated from the Mac address. We’ll also do that on interface fast 20 as well, which is on the 2001 DB 864 network.

So looking at the commands, we go on to interface fast zero slash zero on R one and we say IPV six address 2001 colon DB eight, colon zero, colon one, double colon 64. So that’s the network portion of the address that’s going to be on that interface and then a space. And then we say Eui 64. And for interface fast 20, IPV six address, 2001 DB 80, double colon 64, Eui 64. And the router will now generate IPV six addresses for itself on those interfaces to check that it is working as expected. Well, first we’ll check the Mac address that was on those interfaces. So we do a show interface faster and we can see that the Mac address there is CA zero one two F 240. If we then do a show IPV six interface brief, I can see that the address on fast zero is 2001 DB 80 one, which was the network portion of the address that we configured. And then it’s automatically configured the host portion derived from the Mac address.

So that is C eight because the 7th bit is inverted. So it makes it C eight rather than CA, and then one, and then two F, then the Ffffe is injected and then 240. So you can see that it derived it from the Mac address. And the same thing happened for Interface Fast 20 as well. So that’s how Eui 64 addresses work. If you configure this on a non Ethernet interface on the router, like a serial interface, it will borrow the Mac address from the first Ethernet port. And it’s not recommended to do this. Do not use Eui 64 addresses on your router interfaces. Because if we look at the lab topology diagram here, here is where we have configured manual addresses.

So you see that R one is using colon one at the end of its addresses. R two is using colon two. This is going to make things much more logical and much easier for troubleshooting. You don’t want your routers to have random IP addresses, which is what’s going to happen if you use Eui 64 addresses. So if you’re thinking, well, why tell us about Eui 64 if it’s never used anyway? But where it is useful is for your end hosts. If you’ve got an end host like a normal desktop PC that is going to be running IPV six, you don’t want to have to configure IPV six addresses on every single end host. So we can use DHCP for that like we do in IPV four, or we can use a feature called Slack which automatically generates the address on the interface. And we’re going to cover that in a lot more detail in a later lecture in this section. But for now, let’s see how we configure it on a Cisco router. So in the earlier lab demo, we configured the interfaces on the link between R one and R two.

Let’s now configure the interfaces between R two and R three. So on Fast 10 and R two, and on Fast 10 and R three I will configure them with an IPV six address, but I’ll use Eui 64 rather than using a manually defined address. So let’s jump onto the lab. I’m on R two here and if I do a show IPV six interface brief, you see that okay, I’ve removed all of the IPV six addresses for now. That’s fine, we’ll just do the interface facing towards R three for now. So I’ll go to global configuration, make sure that IPV six unicast routing is enabled. And the subnet on here is I’m just looking at that in my diagram. I need to go to the interface first actually. So let’s go interface Fast 10 and it’s IPV six address 2001 DB eight is the subnet on the link between R two and R three. Normally I would put in the manually defined full IPV six address here, but I’ll use Eui 64 here. So at this point I’ll say double coulon 64.

That is the network portion of the address on this link. And then a space and then Eui 64 and the address will be automatically generated for me. And then I’ll do a no shutdown on here. And now, if I do a Show interface fast 10, you can see there is the Mac address. And if I now do a Show IPV six interface brief, then there is the automatically generated Eui 64 address, which is based on the Mac address that is on that interface. Okay, I don’t actually need to show you, you know, that I could do the same thing over on the other side on R three as well. And then I would be able to ping I would have connectivity between R Two and R three. But if I went on R three and I wanted to ping R two, I would have to ping it by this great big long address here. So don’t use Eui 64 addresses on your routers. It would be much better to use the manually defined address 2001 DB 80 two, double cool on one or double call on two. It’s much more memorable and it’s easier for troubleshooting. Okay, so that was Eui 64. You will see more of it when we get to that slack lesson coming up later in this section.