check_dhcp from nagios host

[Chris Wilson]

Hi Robert,

On Mon, 2005-04-18 at 23:38, Robert Fitzpatrick wrote:
> I found a few people in the past with this problem, but could not find a
> solution. While check_dhcp works fine from one machine on the network,
> when I try to move the Nagios host to the same server, I get the
> standard 'DHCP problem: No DHCPOFFERs were received.'. Does anyone know
> what causes this or how to get it working on the same server?

Some DHCP servers have BIG issues with a DHCP client running on the same
boix and trying to request an address from them. ISC DHCPD is one, and
if you're running it, I recommend that you don't even try to test DHCP
from the same machine, unless you're a C programmer and you fancy
hacking around with its internals.

The problem is that Linux (and probably other *nixes) will send traffic
to itself over the loopback interface, regardless of which interface the
destination address is configured on. But ISC DHCPD doesn't listen on
loopback, and if it did, it would be confused by the same subnet being
on both interfaces (because it treats them as separate).

Hope this helps,

Cheers, Chris.
-- 
(aidworld) chris wilson | chief engineer (chris at aidworld.org)



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