The second step consists of setting the seventh bit of the 64 bit address.
This bit identifies the 48 bit MAC addresses uniqueness or lack thereof.
An Ethernet address has two significances.
It's either globally managed or locally managed.
Globally managed means that you use the Vendor Mac address.
Locally managed means that you rewrite the MAC address with your own value.
In other words, you change the MAC address to a locally significant value.
So that seventh bit or the UL bit is set to either one, which means the address is unique or set to
zero, meaning the address is not unique.
Now in this example, let's assume that we are using a vendor Mac address.
So in other words, this bit gets set to one.
If you have a binary value of six zeros, followed by a one followed by zero, converting that back
to hexadecimal will give you a value of zero two.
So just to reiterate, you have a hexadecimal value of zero zero that's converted into binary.
The seventh binary bit is either set to one or zero, depending whether it's globally unique or not
globally unique that is then converted back to hexadecimal.
So once again, our IPV six aggregate global unicast address is 128 bits in length.
Half of the address is the network prefix, which is 64 bits and half of the addresses.
The interface identifier, which is 64 bits.
The network prefix is broken up into two major parts.
You have the global routing prefix, which is used for the public topology.
In other words, the internet and the subnet ID, which is used for the site topology.
In other words, the subnet portion of the address would be used to create subnets within an enterprise
or within an organization or within a site.
It's 16 bits in length.
That means that a service provider will give you a slash 48 subnet for every site or organization that
you manage.
That gives you 16 bits for subnets, which allows you to create 65,536 subnets within your organization
from one subnet given to you by the service provider.
You would continue using a slash 64 mask on every link, no matter whether it's a point to point link
or an Ethernet subnet.
The service provider network consists of a slash 48 network.
Your internal networks consist of slash 64 subnets.
So once again, the ISP will allocate you a slash 48 subnet.
You will allocate a slash 64 subnet to each interface.
Once again, no need to do complicated sub all your subnets or slash 60 fours from the slash 48 that
you were allocated by your service provider.
Remember, there is no net all internal addresses within your organization.
By using these IPV six aggregate global unicast addresses, which are the equivalent of public IP addresses
within IP version four.
The IP version six address is actually broken up into more fields.
I wouldn't worry too much about this, but I just want to show you the actual format for this aggregated
global unicast address.
You firstly have the interface identifier, which is 64 bits in length.
I've explained that that identifies the equivalent of the host portion in an IP version for address.
The next part is the SLA, ID or site level aggregation identifier.
This is like your subnet identifier, which represents subnets within an organization.
It's 16 bits in length, giving you over 65,000 subnets to use within a site or an organization.
Then you have the MNLA ID, which is the next level aggregation identifier and this would be used by
your ISPs.
There are eight reserved bits which are not currently used and then you have the TLA ID, which is the
top level aggregation identifier used by various regional internet registries around the world.
The internet registries will then assign TLA IDs to large ISPs, specifically transit providers and
exchanges.
And then lastly, we have the format prefix, which is set to 001.
Once again, this portion of the address is the public topology, and we're not particularly concerned
with that.
In this course within enterprises or sites, we would have the subnet ID, which is used for site topology,
and then once again the interface ID, which is used as the host portion of an IPV six address.
The advantage of this IPV six address layout is aggregation.
It allows for aggregation or summarization of addresses within the global internet.
Just be aware as well that every IPV six interface contains at least one loopback address, which is
colon colon 1/1 28.
Optionally, interfaces might include multiple, unique local and global addresses.
This is an important concept.
In IP version four on a Cisco router, you can only allocate a single IP address as the primary IP address
on that interface.
All subsequent IP addresses are configured as secondary IP addresses.
However, in IP version six, you can configure multiple primary IP addresses on an interface.
So that's quite a major change from IP version four.
I'll show you in a moment.
When you enable IPV six, when a Cisco routers interface, multiple IP addresses are automatically allocated
to that interface.
And once again, the whole reason for this address layout is aggregation and summarization.
So let's look at global aggregation.
An Internet registry will have, for instance, a slash 16 address.
So 2001 colon, colon slash 16, a slash 32 subnet is allocated to an ISP.
So in this example, 2001 colon, one, two, three, four colon, colon slash 32 is allocated, let's
say, for instance, to this ISP.
The service provider can then allocate a slash 48 subnet to an organization or enterprise.
So in this example, let's assume that 2001 colon one, two, three for colon, one colon, colon slash
48 is allocated to customer A that customer can then subnet the slash 48 to slash 64 subnets and allocate
those subnets to every interface within the organization.
So notice year 2001, one, two, three, four, Colon one, which is a slash 48 subnet, the enterprise
was allocated is subnet ID again to colon to colon colon.
In other words, a slash 64 subnet is allocated to this interface.
And then notice over here three is allocated to this interface or link.
Just to help you once again with these addresses, remember these values on hexadecimal, a single value
in hex equates to for binary bits.
So we have one, two, three, four hexadecimal values here for hex values times four gives you 16 binary
bits.
So this is actually a 16 bit address, hence slash 16.
By the same token here, remember, this is 16 and this is 16.
So the values between the colons are 16 bit values.
So 16 plus 16 gives you 32, so hence slash 32.
Once again, here we have another value between colons.
So it's 16, 16 and 16.
Remember, leading zeros can be dropped in an address.
So that gives you 48 bits, hence slash 48.
And lastly, this address there is one, two, three, four values between colons leading zeros have
been dropped.
So that's four times 16 giving you slash 64.
I hope that helps you decipher the address a little easier.
Please note on these subnets we have not displayed the host portion of the address.
Now, without further ado, let's set up a basic IP version six network.
In this example, I have router one and router two.
Both routers have a fast Ethernet interface.
Rather, one's network on the first Ethernet interface is going to be 2001 colon.
One colon, one colon, one router two's FOSS Ethernet subnet is going to be 2001 colon one colon one
colon three.
The routers are connected by a serial link and the subnet here is going to be 2001 colon, one colon,
one colon, two.
Notice once again, the subnet mask is always slash 64 on all subnets.
Okay.
So on router one, I'm going to break out of the initial configuration dialog.
Go into global config mode and give the router a name.
And then I'm going to enable IPV six.
Uni costs routing.
So that we can run IPV six on this router.
And then I'm going to go on to f00, the first Ethernet interface.
And give it an address.
So IPV six And notice there are a lot of options here, but I'm going to specify address and then I'm
going to specify an IPV six address.
So 2001.
And in this case, I'm going to give the interface and address of one.
So it's as simple as that to configure an IP version six address on a router.
This portion is the network portion.
And notice we've got colon.
Colon.
So there are a bunch of zeros not displayed here.
And we ending in a one.
And then I can know.
Shut the interface.
And as you can see, the interface has come up.
So now I can type do ping 2001.
And ping the IP address.
And as you can see, the ping is successful on the serial zero interface.
I can do the same thing.
IPV six.
Address 2001.
And on this side, I'm giving it an address of colon one.
And on this side, I'm going to give it an address of Colon two.
So in order to do the same thing, enable IPV six unicast routing.
And then on f00, give it an IPV six address.
Of 2001.
No.
Shut the interface and serial zero zero.
Give it an address.
And I shot that interface.
So hopefully now from router to I should be able to ping router one.
That doesn't work because I forgot to know.
Shut the interface on the side so I'll know, shut it and go back to router two and let's see if the
ping succeeds this time.
The interface came up and as you can see, the ping succeeded.
It's as simple as that to configure IP addresses on a Cisco router.
Now on the first Ethernet interface, I could give it another IP address.
I could say IPv6 address.
Let's just be lazy.
Let's give it an address of 2001.
Colon, colon one slash 64.
And as you can see, the right is accepted.
That address on the right.
I could not ping 2001 colon.
Colon one.
And as you can see, the ping succeeds.
If I could go back onto the interface and give it an address as follows IPV six address and let's say
2001 colon, two colon, colon.
Notice it gives you the option of link local address, but we don't want to do that.
Let's go for slash 64 notice, please.
I haven't put a host portion on this address.
I've just specified the network portion.
And now what I can do is I can specify UI 64 and hit enter.
So we're going to use the MAC address as part of that address.
So now I can type the command show run interface if zero zero to show you the configuration.
And as you can see, there's no IP version for address configured on this interface.
There are only IP version six addresses and they are three IP version six addresses that we have manually
configured.
I could then tap show interface if 0/0.
The Mac address of this interface is c4010fe8 followed by four zeros.
So the vendor portion of this address is c4010f and the unique portion is E eight followed by four zeros.
So just to display that nicely, I'm going to say show interface if zero zero type include BIA.
So it only shows that MAC address in the output.
And there it is.
And then I'm going to type show IPV six interface if zero zero and only include the addresses that we
configured and they are the three IP addresses we configured on the interface.
So notice yes, please.
We'll start from the right.
Inside the unique portion of the Mac address is E eight followed by four zeros.
There it is in the IP address.
Remember, leading zeros can be dropped.
So this zero here represents those four zeros e eight.
Is the eat over there.
F f f.
E has been inserted in the address to make it 64 bits and then notice the remaining portion is c4010f,
which is represented here as c601f.
Once again, leading zeros can be removed.
Notice the zero in front of this f has been removed.
Si 401 has been converted to c601 because the seventh bit has been changed to a one to represent that
this Mac address is globally unique.
So notice a IP address.
Is derived.
From the Mac address by using the UI representation of the MAC address.