Double DHCPDISCOVER ends with DHCPNAK

[Bruce Hudson]

>> 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