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We have all of our systems set up to do internal DNS to a local name server and a secondary name server so that in the event the local DNS server is down they should go over the WAN to the secondary that is up in a remote location.

During a recent maintenance window the primary name server locally was taken offline and our UNIX/Linux systems with Veritas Cluster (VCS) and Red hat cluster both experienced issues with cluster resources.

Trying to determine how long resolution should be delayed when the servers have to go to the secondary (i.e. how long is the timeout to the primary) as it seems to hang for a while if the primary server is there but hung up? Is the length of time it waits before moving to the seconday tunable? This is for Solaris 10 and RHEL 6.

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The timeout is configurable in /etc/resolv.conf with the timeout parameter.

Try adding the line: option timeout:<desired timeout in seconds> to /etc/resolv.conf.

From resolv.conf man page:

      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>).  The value for this option is silently capped to 30.

Credits go to http://www.linuxquestions.org/questions/linux-general-1/linux-dns-resolution-timeout-869229/.

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The Solaris 10 resolv.h shows 5 seconds as default timeout and 2 tries default. The timeout value doubles on each retry, so the default Solaris settings would not move on to the next nameserver until 15 seconds have passed in fruitless querying (5 secs for the first attempt plus 10 secs for the second). Whether or not any particular application will be amenable to waiting that 15 seconds without complaining is anyone’s guess. –  user40397 Jun 4 '13 at 19:08
    
The user experience is definitely worse if each DNS request lasts 15 seconds more than usual, that's a sure thing. For uninteractive applications, it's harder to tell, indeed. –  lgeorget Jun 4 '13 at 21:18
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