Two different IP addresses leased out to the same device

Simon Hobson dhcp1 at
Thu Sep 10 08:08:41 UTC 2009

Markus Zuercher wrote:

>  > This is a longstanding issue when a machine boots with multiple 
>DHCP clients
>>  - and it's mostly down to Microsoft that the problem exists. The RFC doesn't
>>  specify what should be in the Client-ID, and Microsoft decided that putting
>>  the MAC address in there made sense. This isn't wrong, just different to
>>  everyone else who default to not supplying a Client-ID at all.
>Hmm, If I understand you correct, the client's PXE client first
>acquired an IP address, supplied a Client-ID and then Windows did the
>same thing without a Client-ID? I think it would help to not save the
>Client-ID in the lease database - is this correct?

Other way round - it's Windows that supplies a client-id, as far as I 
know it's the only client that defaults to supplying one.

>  > A proposed feature that I believe never made it was to allow the
>>  administrator to configure the database key - it currently defaults to
>>  "pick-first(client-id, hardware)". If changed to just plain "hardware" then
>>  Client-ID would be ignored.
>Looks like this is in the program code, right? Is there anything I can
>do in my server config to get the same effect?

Not at the moment. As I understand it, it was a proposed feature but 
it didn't make it into the code.

Simon Hobson

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