How to get duid from odhcp6c...?

Installing and Using OpenWrt
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I must be missing something, because this seems such a basic Q, but I'm totally exasperated searching for the answer - can anyone tell me how to retrieve my router's duid?

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This seems to suggest that it might be 000300012ab34cd56ef if 12:ab:34:cd:56:ef is my MAC but that seem very short.

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Looks right. All my OpenWrt devices have that same form 0003 0001 <mac>.

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Section 11 of RFC8415 describes how to form different kinds of DUIDs.

3 Likes
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Thanks @efahl , that's just the sort of affirmative statement I needed - I'll run it up the flagpole and see if dnsmasq salutes.

(Edit: opps, dropped a zero, it should have been 0003000112ab34cd56ef)

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Thanks @mk24 - I actually found very similar words here:

And these sort of words just gives me the screaming meemies

'containing a DUID type of 3 and a 2-octet network hardware type code, followed by the link-layer address of any one network interface'

To me that says a string like this 000300012ab34cd56ef (a type 3) and 12ab (again, a 2-octet network hardware type code) and 12ab34cd56ef (again, 'followed by the link-layer address') - it just seems like circular garbage to me... No doubt, I have some brick bats due...

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Not sure what you are trying to say, but 0001 is the 2-octet hardware type in your example. The rest is the "link-layer address", which is a 6-byte mac address for hardware type 1 ("ethernet").

The possible hardware types are those defined for arp, but it's hard to imagine anything other than ethernet nowadays. I would not be surprised if some dhcpv6 implemenations choke on a type 3 DUID with a length different from 10 octets.

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Thanks @bmork - I was trying to say the definition in the RFC seems unintelligible - but, your explanation is very helpful, thank you.

So, to clarify, there's the 0001 2-octet hardware type which is the last 4 digits of the odhcp6c default given here and means 'ethernet' plus the ethernet address 12ab34cd56ef, which gives 000112ab34cd56ef - but there's still the first 4 digits of the odhcp6c default unexplained: 0003. Would I be correct to assume that means the address is an address of 'type 3'?

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