[CentOS] DNS lookup delay with centos & postfix

[Tom Brown]

Does dig use libresolv or read directly from resolv.conf? Also do you have a timeout configured in resolv.conf or are you relying on the os default?

On 25 Jul 2012, at 21:57, Steve Lindemann <steve at marmot.org> wrote:

> I'm a bit baffled by this and I'm looking for ideas...
> 
> background:
> two DNS servers (ns1 & ns2)(64bit CentOS 5.8)
> one email server (64bit CentOS 5.8 & postfix 2.3.3)
> one nagios server (64bit CentOS 5.8 & nagios 3.3.1)
> 
> situation:
> - all servers configured to use both DNS servers for lookups
> - ns1 server down for hardware problem
> - nagios alerts that smtp on email server taking longer than 2 seconds 
> to respond
> - nagios alert for smtp on email server clears when ns1 returns to service
> 
> - when I use dig from the email server command line there is no problem 
> or delay when ns1 is offline.  It worked without a hitch using ns2.
> 
> Anyone have any ideas for why nagios would have trouble testing smtp on 
> the email server when the primary dns goes offline?  I'm not even sure 
> where to look or who else would make sense to ask the question of on 
> this one.  I'd appreciate any insight anyone out there has on this.
> -- 
> Steve
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