handle duplicate client identifier

[Stefan Düring]

Hi,

I'm running isc-dhcpd-4.1-ESV-R and encounter problems with Ubuntu 18.04
clients.

These clients have of course different MAC addresses. But because they
were cloned from a single image, they own all the same machine-id which
used for the "client-identifier" that is sent to the dhcp server.

The server should assign the ips dynamically but it assigns the same ip
address to every client due to the identical "client-identiier".

Ok, it should be possible, and maybe the best way, to make the
machine-id unique on every client. But my question is, if there is a way
to prevent the server to use the client-identifier as a key instead of
MAC address ?

Thanks



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[sthaug]

> Ok, it should be possible, and maybe the best way, to make the
> machine-id unique on every client. But my question is, if there is a
> way to prevent the server to use the client-identifier as a key
> instead of MAC address ?

In newer versions of ISC DHCP you have "ignore-client-uids" available.
Not sure if this exists in your version.

Steinar Haug, Nethelp consulting, [hidden email]
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[glenn.satchell]

With Ubuntu Xenial you can remove /etc/machine-id when cloning the
system and it will be re-created with a new unique value on first boot.
Similarly once systems are running you can remove the file and reboot.
See machine-id(5) man page.

Otherwise as Steinar says add

ignore-client-uids true;

dhcpd.conf(5) man page will contain details if it is valid in your
version.

regards,
-glenn

On 2019-06-14 16:44, [hidden email] wrote:

>> Ok, it should be possible, and maybe the best way, to make the
>> machine-id unique on every client. But my question is, if there is a
>> way to prevent the server to use the client-identifier as a key
>> instead of MAC address ?
>
> In newer versions of ISC DHCP you have "ignore-client-uids" available.
> Not sure if this exists in your version.
>
> Steinar Haug, Nethelp consulting, [hidden email]
> _______________________________________________
> dhcp-users mailing list
> [hidden email]
> https://lists.isc.org/mailman/listinfo/dhcp-users

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