dhcp server issues its own address

S Kalyanasundaram skalyanasundaram at novell.com
Mon Apr 16 10:55:18 UTC 2007

Thanks simon,
   Just wanted a clarification, since there is no free lease it took the abandon lease and issued. Since in the first time it is able to identify the ip is exist in the network by pinging, why cant it do in the next time. Abandon the IP again and say no free lease again. Why the reclaimed address is not followed as like other free lease, it just issued with out any check like what is done earlier?

Is there any time gap to reclaim the abandoned  IP address?

Thanks for your help,

>>> On Fri, Apr 13, 2007 at  5:03 PM, in message
<a06230902c24519a9042f at simon.thehobsons.co.uk>, Simon Hobson
<dhcp1 at thehobsons.co.uk> wrote: 
> S Kalyanasundaram wrote:
>>Hi all,
>>I have got something buggy. I don't know whats wrong.
>>I had my configuration file as simply
>>ddns- update- style none;
>>subnet netmask {
>>  range;
>>This IP is belong to the machine where the dhcp server is running 
>>and i started the "dhcpcd" from another machine. Both are isolated 
>>machines and connected together.
>>I have got the following logs from the server.
>>DHCPREQUEST for from 00:03:47:1f:3d:e2 via eth0: 
>>unknown lease
>>DHCPREQUEST for from 00:03:47:1f:3d:e2 via eth0: 
>>unknown lease
>>DHCPDISCOVER from 00:03:47:1f:3d:e2 via eth0
>>ICMP Echo reply while lease valid.
>>Abandoning IP address pinged before offer
>>Reclaiming abandoned lease
>>DHCPDISCOVER from 00:03:47:1f:3d:e2 via eth0
>>DHCPOFFER on to 00:03:47:1f:3d:e2 via eth0
>>DHCPREQUEST for ( from 00:03:47:1f:3d:e2 via 
> eth0
>>DHCPACK on to 00:03:47:1f:3d:e2 via eth0
>>I am wondering how the dhcp server can issue its own address to the 
>>client. It first said abandoning and reclaiming and after that it 
>>issued. I am using dhcp v3.0.3. Now the client also shows the IP 
>>same as which dhcp server's machine has.
>>Is there anything to do with client so that he sends NACK to server 
>>to abandon again?
> Problem is simple, you configured the server to give out an address 
> that wasn't suitable. It abandoned it because first time around the 
> 'last ditch sanity check' of ping before offer detected that the 
> address was in use. Next time around it recovered the address and 
> issued it.
> The client MAY or MAY NOT detect that the address is in use and 
> decline the lease, but the server should not rely on that.
> The answer is that this is a PICNIC error -  problem in chair, not in 
> computer. DON'T tell you server to give out addresses it shouldn't 
> give out ! The ISC server does not check for all possible 
> misconfigurations, the administrator is expected to know what he is 
> doing.

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