weird case for IP duplicated on LAN

Sten Carlsen stenc at
Sun Feb 22 22:33:43 UTC 2015

On 22/02/15 20:32, IT Support wrote:
> Hi
> Thanks Nial for your answer, about logs, just I can see this:
> dhcpd: DHCPDISCOVER from 00:88:88:88:88:88 via
> dhcpd: DHCPOFFER on to 00:88:88:88:88:88 via
> Hi Sten about your answer:
> Suggest you look for a ClientID in both hosts, probably the same.
> How can I check the ClientID?
I dhcpd.leases file it is marked by uid for each lease. The line is
missing if there is no ClientID.

If two different MAC addresses ask for an IP but present the same
ClientID, they are treated like the same host and given the same ID.

The answer is in the dhcpd.leases file.
> On 02/22/2015 02:42 PM, Sten Carlsen wrote:
>> Suggest you look for a ClientID in both hosts, probably the same.
>> ClientID takes precedence over MAC if present. (There are options to fix
>> this).
>> On 22/02/15 19:35, IT Support wrote:
>>> On 02/20/2015 12:17 PM, IT Support wrote:
>>>> Hi eveyone. I'm facing a weird case of IP duplicated on my LAN, ISC
>>>> DHCPd version 4.1.1 running on Debian, this is the case. For example
>>>> user A already got an IP address from dhcp server (
>>>> 'till here everything goes ok.  Then user B get connected to the LAN,
>>>> asking for an IP address to dhcp server, assigning the same IP address
>>>> to the user A ( creating an IP address conflict.
>>>      Please someone to throw me a bone here?
>>> Thanks in advance.
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Best regards

Sten Carlsen

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