check_dns works fine for half my servers, fails for other half

[Marc Powell]

> -----Original Message-----
> From: nagios-users-bounces at lists.sourceforge.net [mailto:nagios-users-
> bounces at lists.sourceforge.net] On Behalf Of Sean Schertell
> Sent: Friday, August 31, 2007 8:05 PM
> To: Nagios-users at lists.sourceforge.net
> Subject: [Nagios-users] check_dns works fine for half my servers,fails
for
> other half
> 
> I'm not really a DNS guru, so it's probably an obvious thing -- would
> someone mind enlightening me as to why this happens? How come it
> works fine for the first server but fails for the second? Their
> definitely both running DNS.
> 
> [root at turnip etc]# /usr/local/nagios/libexec/check_dns -H
> microsoft.com -s rosemary.datafly.net
> DNS OK: 0.324 seconds response time. microsoft.com returns
> 207.46.197.32,207.46.232.182|time=0.323644s;;;0.000000
> 
> [root at turnip etc]# /usr/local/nagios/libexec/check_dns -H
> microsoft.com -s nutmeg.datafly.net
> DNS CRITICAL - '/usr/bin/nslookup -sil' msg parsing exited with no
> address

nutmeg is returning output from nslookup that check_dns can't parse. It
would appear that nutmeg isn't configured to perform recursive lookups
(lookups for domains it doesn't host) and you're expecting it to. 

$ nslookup -sil microsoft.com rosemary.datafly.net
Server:         rosemary.datafly.net
Address:        64.34.193.57#53

Non-authoritative answer:
Name:   microsoft.com
Address: 207.46.232.182
Name:   microsoft.com
Address: 207.46.197.32

$ nslookup -sil microsoft.com nutmeg.datafly.net
Server:         nutmeg.datafly.net
Address:        72.36.130.114#53

Non-authoritative answer:
*** Can't find microsoft.com: No answer

As an aside, you shouldn't be allowing me to perform recursive lookups
with your servers anyway. Rosemary could easily be hijacked to perform
DNS based DOS attacks.

-
Marc

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