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I would like to assign a static IPv6 address to my machine running Ubuntu Server 15 using DHCPv6. To do so, I need to know the DUID used by the DHCP client so I can assign the static IP to it in my network's DHCP server.

How can I find out which DUID is being used?

2 Answers 2

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Ubuntu server calls dhclient with a few flags, but mostly default options, and it therefore defaults to a type 1 DUID-LLT DUID. Ubuntu desktop uses Network Manager which then calls dhclient with a type 4 DUID-UUID DUID.

For servers, it puts it in /var/lib/dhcp/dhclient6.......lease
For desktop, it puts it in /var/lib/NetworkManager/dhclient6.......lease

It's a weird string that looks like:
default-duid "\000\001\000\001\037\305\371\341\001\002\003\004\005\006"

Here's a short script you can use to convert it to a normal hex format duid.
Just run the script like:

./script '\000\001\000\001\037\305\371\341\001\002\003\004\005\006'

The script:

#!/bin/bash

printf $1 | hexdump -e '14/1 "%02x " "\n"' | sed 's/ /:/g'
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  • my dhclient6..lease file has the following: "\000\004\354\352~\365\017\375\330\201!\230+<Oj\031\302" which returns an error with your script. Any ideas?
    – Arindrew
    Feb 21, 2017 at 18:09
  • 1
    Replace the double quotes with single quotes because there are characters like ! in your duid lease file and change the 14/1 to 18/1 in the script to account for the longer length of type 4 duid's. I think the script originally came from some redhat documentation and only had type 1 and type 3 duid's in mind. Feb 22, 2017 at 7:57
  • actually, I found even better was to add -s 2 to skip some of the pre-amble, e.g.: hexdump -s 2 -e '14/1 "%02x " "\n"' /var/lib/dhcpv6/dhcp6c_duid Jul 9, 2017 at 7:49
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If you are using DHCP with ISC dhcpd look in:

/etc/dhcp/dhclient6.conf


If you are using dibbler as dhcp client check for the DUID in:

/var/lib/dibbler/client-duid

It might also be worth checking in /etc/dibbler/client.conf if any other bits are there.

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