How to find DUID on Lion

I may be misreading it, but the Wiki article you linked to state that a DUID is:

The DHCP Unique Identifier (DUID) is used by a client to get an IP address from a DHCPv6 server.

So breaking it down, DHCP is DUID. Which means an automatically assigned IP address. To manually enter the DUID (DHCP address), you change Automatically to Manually.

Since your PC is being assigned an IPv6 address, the Mac should be too, unless you have something turned off to prevent it.

Do you not see this under TCP/IP in the Ethernet settings?

Even though Automatically is on, my Mac doesn't have an IPv6 address since v6 DHCP is turned off at the router. If it were on, it would show both numbers being assigned to my Mac.

Anyway, it's not a number you can find unless it's being assigned by the router, or your Internet provider.

Which is another thought. If you have a DSL or cable modem connected directly to the Windows computer, then yes, it will have a v6 address (assigned by the remote IP server) and the Mac will not since the IP provider doesn't even know the Mac exists (no connection).

Okay. Well, I could turn IPv6 on at the router and set it to DHCP. Then (after restarting the router, and then the Mac), the System Preferences would tell me what address was assigned to it. I could also turn on IPv6 for external connection so talks to my DSL modem as IPv6 rather than IPv4. Right now, both are blank for IPv6 since it's disabled.

But anyway, you won't see one unless it's enabled on your router.

Wait a minute. Let's start over. You said:

I want to use IPv6 on iMac with Lion but I need assign static IPv6 address.

A static address is your DUID. You don't find it, you already have it. I presume the fixed address is a university, your IP provider, etc. has already given you the address and other info to enter?

If so, go into the System Preferences and click on Network. Choose the active Ethernet port at the left, then click on Advanced. Under the TCP/IP tab, where the pull down menu for Configure IPv6 is, change Automatically to Manually. Enter the Router, IPv6 Address, and Prefix Length you were given. Click OK, then click Apply.

So DHCP is not DUID

Partly. That's why it's in parentheses right after the written term:

The DHCP Unique Identifier (DUID)

As in, DHCP Unique Identifier.

it's a client ID

Yes, and looking further, I see what you mean. Calling DUID the same as DHCP is not correct. But it is somewhat similar. The difficult part is finding anything on the web that explains it simply. This one is pretty good. To say DUID is confusing is putting it mildly. A few excerpts:

Each interface has an ID, called IAID – Interface Association Identifier – that is a binding between the interface and one or several IP addresses. Each allocation in the DHCPv6 server is identified by a DUID and a IAID. The question is how these are created. It’s not the same as the mac address, but can be based on it.

The DUID is supposed to be stored in permanent storage, not to be changed during a products lifetime.

That's clear. the DUID is supposed to be a permanent value on the machine. But then they muddy that statement right afterwards with:

The problem is of course that it will be very hard to determine the DUID for a device beforehand.

If the DUID is a fixed, "not to be changed" value, then how can it be hard to determine what it is?

Oodles of information on it here, if you can make sense of it.

I guess the main question is, why do you need IPv6? If all you're doing is connecting to the Internet, IPv4 is all you need. IPv6 is just a massively larger pool of addresses. It doesn't really have any other benefit. It won't make your connection go any faster.

Edit: Though I just now noticed I had somehow ended up in the Server forum rather that the client ML forum. I thought you were just talking about simpler home use. So I take it you're required to use IPv6 / DUID as a web server?

It appears that way. I can't find enough about it regarding OS X to say one way or the other for sure.

I tried looking up DUID on both Mountain Lion client, and Lion Server. There isn't one word on the subject in OS X's help files. I was really surprised to find zilch in the Server help topics.

There's this Terminal command:

ipconfig getpacket en1

Since my Mac Pro has two Ethernet ports, en0 would be port 1, and en1 would be port 2. I know my Ethernet cable is connected to port 2, so used en1. However all that shows is what I already know from the Network panel in the System Preferences. What IPv4 address is assigned to my Mac and some other info. In relation to that, there's also:

ipconig getv6packet en1

Which returns nothing. Also what I expected since the Network panel is blank for IPv6.

I haven't checked trevor's links in this topic I found, but they may be useful.

Edit: Hey, something maybe useful after all. Go to this page, and then click on the link, this page to help me select an IPv6 address range. You are led to another page that generates an unused IPv6 you can manually enter.

Do you mean the MAC address? If so, open the System Preferences and click on the Network icon. Click on Advanced, then the Hardware tab. The MAC address is shown on that page.