Clients keep sending DHCPDECLINE

[moffe at zz9.dk]

  Hi again

Thanks for all your suggestions. I started researching the mysterious 
ARP replies. It turned out that the main managed switch (HP Procurve 
8000M) had "Automatic Broadcast Control" enabled. I disabled it and the 
multiple arp replies stopped.

So far no clients sent DHCPDECLINE, but it might be a coincidence still 
(sometime it happens many times a day, sometimes a few days can pass 
without problems).

I still do feel that this might be the problem.

Best regards
/Rasmus

Den 23-08-2010 09:45, Tom Schmitt skrev:
> -------- Original-Nachricht --------
>> Datum: Mon, 23 Aug 2010 09:28:08 +0200
>> Von: moffe at zz9.dk
>> An: Users of ISC DHCP<dhcp-users at lists.isc.org>
>> Betreff: Re: Clients keep sending DHCPDECLINE
>> Hi all
>>
>> Could this be caused by a network loop? I also get multiple ARP replies
>> in many cases like eg. this:
>>
>> 06:21:43.585145 arp who-has 172.31.0.1 tell 172.16.0.2
>> 06:21:43.585288 arp reply 172.31.0.1 is-at 00:23:df:f9:3d:74
>> 06:21:43.585755 arp reply 172.31.0.1 is-at 00:23:df:f9:3d:74
>> 06:21:43.586362 arp reply 172.31.0.1 is-at 00:23:df:f9:3d:74
>>
> Yes, I do think that could be the source of your problems. If you have a problem in your routerconfiguration (like two HSRP-interfaces, both acting as active) or someone else in the subnet, acting as a router (maybe via wlan), then some traffic can easily getting multiplied.
>
> This could explain the DHCPDECLINES:
> The client is sending it's ARP request to see if someone has this IP already. Through the network-loop the client is receiving it's own ARP-request and interprete it in a form, that someone seems to claim this address, so it will be in use in short time. Ergo the client is sending the DHCPDECLINE, hoping to get an answer were nobody else is claiming the IP.
>
> Tom.


-- 
Rasmus Bøg Hansen || http://www.zz9.dk/
moffe at zz9.dk      ||