Nagios checks and DNS queries

[Steve Burton]

Sean McAfee wrote:
> Steve Burton wrote:
>   
>> Dirk,
>>
>> my solution was to run a slave name server on the Nagios server itself , 
>> restricted to only answer queries from localhost.
>>
>> Steve.
>>
>>     
> Why not set something like "options timeout:1 attempts:1" in 
> resolv.conf?  From man resolv.conf:*
>
> timeout:*/n/
> sets the amount of time the resolver will wait for a response from a 
> remote name server before retrying the query via a different name 
> server. Measured in seconds, the default is RES_TIMEOUT (currently 5, 
> see <resolv.h <http://linux.die.net/include/resolv.h>>).*
>
> attempts:*/n/
> sets the number of times the resolver will send a query to its name 
> servers before giving up and returning an error to the calling 
> application. The default is RES_DFLRETRY (currently 2, see <resolv.h 
> <http://linux.die.net/include/resolv.h>>).
>
> With the defaults, you're looking at 10 seconds (2 attempts, 5s apart) 
> before it moves onto the next server.  Since 10 seconds is the default 
> timeout for those checks, you'll always hit a timeout unless the DNS 
> server becomes responsive again.
>
>   
Sean,

I reason I set up the slave server was so my nagios instance could 
monitor the 'real' DNS servers by name and check the host and other 
services on those hosts (they're Windows DCs) even if (or especially if) 
the DNS service had failed.

Steve.


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