dhcpack instead dhcpnak

[Steven Carr]

So if you are still seeing just a DHCPREQUEST from the client then it
doesn't look like the client has issued a DHCPRELEASE (the release
should also be logged in syslog). What client are you seeing this on?
if it's Windows you need to run "ipconfig /release" before you run
"ipconfig /renew".

Steve

On 29 May 2013 11:36, benek <zbyszek.r at retsat1.com.pl> wrote:
> Thanks for your reply. Unfortunately, even when I do a lease renewal or
> change subnet in syslogu I see that the DHCPREQUEST message is sent :( and
> host skips an entry in dhcpd.conf and gets the "old" ip address "from
> nowhere". Only when I change the mac, host sends a DHCPDISCOVER and gets a
> new address. It is looks like a some kind of cache, in which is an array of
> mac (maybe arp table ?) send/relay the queries and it causes this problem.
> And I still don't understand how it's happens.
>
> ----- Original Message ----- From: "Steven Carr" <sjcarr at gmail.com>
> To: "Users of ISC DHCP" <dhcp-users at lists.isc.org>
> Sent: Tuesday, May 28, 2013 7:17 PM
> Subject: Re: dhcpack instead dhcpnak
>
>
>
>> If the client already has the lease and it is requesting a renew then
>> they DHCP server will acknowledge the renew request and the client
>> will continue to use the address indefinitely, as far as the DHCP
>> server is concerned the leases file says the client has a lease for
>> that IP address and will skip looking at the config part. Only if the
>> lease has expired and the client performs a DHCPDISCOVER will the DHCP
>> server look at the configuration and give the client the different
>> address.
>>
>> You can't really prevent this other than don't change the IP address
>> to another address in the same subnet. The workaround is that you will
>> need to force the client to release it's current IP address then
>> request a new address.
>>
>>
>>
>> On 28 May 2013 16:11, benek <zbyszek.r at retsat1.com.pl> wrote:
>>>
>>> Hi,
>>> I noticed a strange behavior of the dhcp server (the dhcp3-server 3.1.1-6
>>> +
>>> lenny4 on debian). All users have so defined addresses:
>>> "... the ethernet hardware aa:bb:cc:dd:ee:ff; fixed-address
>>> 10.20.30.40;..."
>>> When I changing the ip address for a given mac in dhcpd.conf sometimes
>>> the
>>> server responds with DHCPACK to the DHCPREQUEST with a non-existent ip
>>> address and the user receives a non-existent settings in dhcpd.conf.
>>> Normally should respond DHCPNAK and force of a new lease process.
>>> What could be causing this behavior and how I can prevent it.
>>>
>>> Regards
>>>
>>> benek
>>> _______________________________________________
>>> dhcp-users mailing list
>>> dhcp-users at lists.isc.org
>>> https://lists.isc.org/mailman/listinfo/dhcp-users
>>
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>
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