MAC vs DUID issue

Valdinei Rodrigues dos Reis valmatrix at
Wed Apr 2 17:27:14 UTC 2014

Hi there,

We are using DHCP to all of our IPv6 clients, fixing the IPv6 address using
the MAC address.
We do not want to use DUID mapping due to a lot of reasons.

Some clients report duplicated IPv6 address, and we strive to find whats
All the clients have a host declaration, we have checked all the MAC
addresses for any typos, and everything is Ok.

After a lot of work, we discovered that the clients had duplicated DUID,
due to our support staff use of clonezilla to deliver the machines to the

Besides, all the communications to the DHCP server is done by dhcp relay,
due to all of our servers be statically configured.

I do not understand why DHCP is associating hosts to DUID, as long as we
make MAC mappings to IPv6 Address. What's happening? It would be my guess
that DHCP server is in someway associating DUID with IPv6 in the first
lease, and prefer the DUID, no matter there is a MAC mapping.

Is there any way to tell DHCP server to ignore DUID or give preference to

Thanks in advance.
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