So now that we've talked a little bit about IPv6,
let's move on and contrast and compare DHCPv4 to DHCPv6,
and then delve into the nuts and bolts of the DHCPv6 protocol
in much the same manner that we did DHCPv4.
First off, DHCPv4 runs on IPv4 and DHCPv6 runs on IPv6.
You know you think you wouldn't have to say that,
but you'd be surprised at the number of people that ask if a
DHCPv6 server can hand out DHCPv4 addresses.
Right now, the answer is no,
although there are some pretty smart people working on a way to try
to make that happen to ease the adoption of IPv6.
That way you can set up an IPv6 server that still manages IP addresses for
your IPv4 network while you're adding on DHCPv6 and IPv6.
Secondly, DHCPv4 uses UDP port 67 for the sever and UPD port 68 for the client.
And as I mentioned in the overview, DHCPv6 uses different UDP Ports,
547 for the server and 546 for the client.
I don't know why they changed the UDP ports.
It might be for some kind of interoperability,
although the IPv4 and IPv6 stacks are completely different,
so, again,
they use different ports and it's important to know that if you're going
to use a firewall to block off some of the traffic or you're going to
use NetFlow to catalog your DHCP traffic.
DHCPv4 uses broadcast packets for its advertisements and leases as we
discussed when we talked about IPv4 and DHCPv4.
DHCPV6 uses multicast packets,
which you'll see in the traffic trace when we look at it here in a bit,
and it uses multicast packets because there are no broadcasts in IPv6.
And finally, DHCPv4 uses the MAC address as the client ID,
whereas DHCPv6 uses something called the DHCPUID,
or the DHCP Unique ID, to uniquely identify both servers and clients.
This is quite simply because many connected devices in today's
world actually has more than one network card.
Back when DHCPv4 was put out,
you had a wired network card in the back of a computer and
that's how you got on the local network,
or the internet once the internet came around.
DHCPv6 with modern devices, I mean just look at your smartphone.
It has a Wi-Fi interface, it has a Bluetooth interface,
it has a 3G, or 4G, or LTE interface,
all with distinct MAC addresses for the particular hardware that they're using.
So if your client is being identified by MAC address,
which MAC address do you use?
And that is the purpose the the DHCP unique ID in DHCPv6.
Now there are four different kinds of DHCP unique IDs.
Three of them are put forth in RFC 3315,
which is one of the founding standards for DHCP for IPv6,
and the fourth is added by RFC 6355.
And again, if you ever need help going to sleep,
go pull out some of the RFCs and sit and read through them.
Although if you're really nerdy like I am,
sometimes you might read them just for fun so that you don't go to sleep.
At any rate, we'll touch on the four types of DHCP unique IDs.
If you want to know more about exactly how they're generated,
again, I reference you to the RFCs.
The first type is LLT, or Link-Layer plus Time.
This a Type 1 DUID and basically the DUID consists of the
modulo of the number of seconds since January 1,
2000,
followed by any valid hardware ID or MAC address that's connected to
the IPv6 network at the time the DUID is generated.
The second is the Type 2 DUID, and it is the DUID-EN, or Enterprise Identifier.
And essentially this is the closest that you get to a MAC
address like you'd have for DHCPv4.
This is the enterprise number for the manufacturer of the
network device that is registered with IANA followed by a
unique identifier assigned by the vendor.
Now where the vendor comes up with these numbers is
completely left up to the vendor,
but they have to be unique and they have to be tied
to the physical network hardware.
Next is the Type 3 DUID called DUID Link-Layer,
and this actually is the MAC address of the physical network card.
It's got the number 3 in the DUID, followed by the hardware type identifier, i.
e.
Ethernet, frame relay, serial, so and so forth,
and then the link-layer address,
which for Ethernet interfaces is the MAC address and again,
for serial interfaces or other type of interfaces,
they have their own link-layer address.
And the last DUID type is the UUID.
This is the newest of the four DUID types and it takes advantage
of newer hardware having a UUID burned into the hardware that can
be used to uniquely identify that workstation or that piece of
equipment on the network.
I keep saying workstation because I'm really old and that
used to be all that was on networks.
You didn't have smartphones and tablets and everything back in the day.
We had two tin cans and a string and we were happy.
Anyway, I'm not really that old, but sometimes I feel that old.
Regardless, those are the four types of DUIDs,
and now that we've gone over those, we will discuss the different flavors of DHCPv6.