[CentOS] how to increase DNS reliability?

[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.