[Nagiosplug-help] check_dhcp across subnets

Scott Machtmes scottm at brocade.com
Fri Mar 14 19:27:48 CET 2008

After running a wireshark trace, I do see the dhcp discover on the 
remote dhcp server. However for some reason the server never sends out 
an offer. I don't see any further transactions from the server to the 
requesting check_dhcp process. Not sure what to make of that because the 
dhcp server does work for it's normal subnet requesting hosts.

Ian Rarity wrote:
> I'd suspect your router, in that case.  Perhaps it's been explicitly
> configured not to forward DHCP packets as well as broadcasts?  You could
> always use Wireshark or something similar to see if the requests are
> actually making it as far as the DHCP server.
> Ta,
> IR.
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> Ian Rarity
> Technical Engineer
> ESPC (UK) Ltd.
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>>>> Scott Machtmes <scottm at brocade.com> 13/03/2008 22:26 >>>
> That's actually what I tried using the -u but it's not working. My dhcp
> servers are windows 2003 servers by the way with no firewalls.
> Ian Rarity wrote:
>>>>> Holger Weiss <holger at CIS.FU-Berlin.DE> 13/03/2008 10:44 >>>
>> Or if you tell check_dhcp to pretend to be a DHCP relay using the
> "-u"
>> flag :-)  It'll then send a normal unicast packet which should be
>> routed
>> as any other packet (unless it's filtered, of course).
>> Ah - I think I need to update my version of the plugins...
>> Ta,
>> IR.
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Scott Machtmes, Sr. Systems Administrator
Engineering Lab Services
1745 Technology Drive
San Jose, Ca. 95110
scottm at brocade.com

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