Can bind be configured to not drop RR's from the cache when the upstream DNS server is unresponsive

Dave Warren davew at
Mon Mar 21 21:34:19 UTC 2016

On 2016-03-19 19:03, Barry Margolin wrote:
> In article <mailman.398.1458363747.73610.bind-users at>,
>   Dave Warren <davew at> wrote:
>> My current logic is that I do a SOA query and check the serial number,
>> if it has changed, I query every needed hostname into a temp file, and
>> if every single query was successful, check the SOA again, and if it
>> still matches, update the /etc/hosts. If anything goes wrong (including
>> a mismatch between the SOA), dump the temp file and try again.
> That's feasible if you can reconfigure all the client machines to do
> this. It's not very scalable if you have a network of machines running
> different operating systems, and you'd like to have your central
> resolver take care of all the caching.

True enough. I only do this on mission critical systems that cannot go 
down (or more likely, cannot be in a situation where they will fail to 
restart) because DNS happens to be down. Ultimately DNS scales very well 
and it's own scaling and caching mechanisms are the best solution most 
of the time, but there are cases where this isn't true, or where you 
need something more persistent than a cache.

Dave Warren

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