[CentOS] how to increase DNS reliability?

Thu Jul 25 13:48:07 UTC 2019
rainer at ultra-secure.de <rainer at ultra-secure.de>

Am 2019-07-25 15:41, schrieb hw:
> On 7/25/19 2:53 PM, rainer at ultra-secure.de wrote:
>> Am 2019-07-25 14:51, schrieb hw:
>>> Hi,
>>> how can DNS reliability, as experienced by clients on the LAN who are
>>> sending queries, be increased?
>>> Would I have to set up some sort of cluster consisting of several
>>> servers all providing DNS services which is reachable under a single
>>> IP address known to the clients?
>>> Just setting up several name servers and making them known to the 
>>> clients
>>> for the clients to automatically switch isn't a good solution because
>>> the clients take their timeouts and users lacking even the most basic
>>> knowledge inevitably panic when the first name server does not answer
>>> queries.
>> Run a local cache (unbound) and enter all your local resolvers as 
>> upstreams.
> That can fail just as well --- or be even worse when the clients can't 
> switch
> over anymore.  I have that and am avoiding to use it for some clients 
> because
> it takes a while for the cache to get updated when I make changes.
> However, if that cache fails, chances are that the internet connection 
> is also
> down in which case it can be troublesome to even get local host names 
> resolved.
> When that happens, trouble is to be expected.

Anything else is - IMHO - much more work, much more complicated and much 
more likely to fail, in a more spectacular way.
Especially all those keepalive "solutions".

I have found that I need to restart unbound if all upstreams had failed.