dhcpack instead dhcpnak

[benek]

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
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