Understanding service checks

[Arno Lehmann]

Hello,

On 3/28/2006 8:01 PM, Dirk H. Schulz wrote:
> Hi folks,
> 
> today both our dns servers went out of function.

Funny day, eh?

> As a result every service check in nagios timed out after 10 sec. and 
> was CRITICAL.
> 
> EVERY one of several hundred!
> 
> Since service check definitions depend on host definitions and host 
> definitions contain ip addresses I would not have expected a dns outage 
> to have any effect on nagios' service checks.
> 
> Can anyone explain why there IS an effect? I would like to understand it 
> more deeply.

Rhis sounds like it depends only on your Nagios setup and your network. 
For example, if you _only_ use IP adresses and not DNS in your Nagios 
configuration, all your routers do _not_ need DNS, and all your services 
do _not_ depend on DNS (think of verifying reverse mapping for mail 
address verification, or SSL certificate checks, for example, or nrpe or 
(x)inetd or TCP wrappers... lots of opportunities to need DNS without 
being aware of it) having a DNS outage should not affect service state.

In other words: Since you experienced service failures, something _must_ 
depend on either DNS or some outage not directly monitored affected DNS 
as well as all other checks you run. Or it's all been a great coincidence...

Arno

> Dirk
> 
> 
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-- 
IT-Service Lehmann                    al at its-lehmann.de
Arno Lehmann                  http://www.its-lehmann.de


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