Double DHCPDISCOVER ends with DHCPNAK

[Glenn Satchell]

On 03/05/11 01:19, Bruce Hudson wrote:
>>> We boot machines over network with TFTP and after the image is
>>> downloaded it starts Ubuntu.
>>>
>>> The problem comes with the DHCPDISCOVER requested in Ubuntu start. The
>>> server offers the same IP offered before, but when the client requests
>>> this IP the server tells that is not available
>
>      Are you using a server modified in any way? The surprising part of this
> scenario, based on version 3 experience as we have not moved to version 4
> yet, is not that the address is unavailable, but that the server offers it
> in the first place.
>
>      According to the protocol, the primary identifier of a client is the
> "client identifier" option. The server uses the MAC address only if there
> is no "client identifier". Normally, if a client makes two requests, one
> with and one without a "client identifier", they are seen by the server as
> separate clients and are given two different IP addresses. This is what
> happens in the PXE boot process. Judging from traffic on this list, it has
> long been an annoyance to some people.
>
>      I suspect somebody has tried to "fix" this behaviour but has not quite
> completed the job. The code to process the discover considers the two cases
> to be equivalent but the code doing the request does not. Whether that
> somebody was at ISC (in which case you should probably file a bug report)
> or modified you copy, I do not know. I would expect the release notes to
> say something if there has been an official change.
> --
> Bruce A. Hudson				| Bruce.Hudson at Dal.CA
> ITS, Networks and Systems		|
> Dalhousie University			|
> Halifax, Nova Scotia, Canada		| (902) 494-3405

Windows definitely behaves that way (setting the client identifier) but 
the OP said they are booting Ubuntu, so I am pretty sure that does not 
set the client identifier. Thus the server would see the request as 
coming from the same client with the given MAC address.

-- 
regards,
-glenn
--
Glenn Satchell                            |  Miss 9: What do you
Uniq Advances Pty Ltd, Sydney Australia   |  do at work Dad?
mailto:glenn.satchell at uniq.com.au         |  Miss 6: He just
http://www.uniq.com.au tel:0409-458-580   |  types random stuff.