Re: help for DNS queries

On Mon, Aug 5, 2019, at 20:32, Paulina wrote:
> > On Mon, Aug 5, 2019, at 06:50, Paulina wrote:
> >>
> >> I have been using a cloud host, it seems I have a unnormal DNS resolver
> >> entry:
> > 
> > And what exactly is unnormal in:
> > 
> >> nameserver 127.0.0.53
> >> options edns0
> > 
> > ???
> 
> Sorry my mistake.
> After checking the documents I just know what's the difference between 
> Caching server and auth-server for DNS queries.

In fact the difference to know about is between a recursive nameserver and an authoritative one
(both services should be separate while historically at least some software like bind
could be configured to do both).
Recursive nameservers have a cache, but this is a side effect.

> So it seems I am using a caching server whose IP addr is 127.0.0.53.

Yes, your system is configured like that.

> But isn't this addr a loopback IP? I was not sure about it.

Yes, everything like 127.x.y.z, so it just means that you have
a recursive nameserver running and listening on your host.
Which is often/most of the time the desired setup in fact.

> I was thinking the caching server should be 8.8.8.8 etc.

A matter of taste and it depends on your configuration also,
if you have to resolve purely internal names.

I dislike it for both technical reasons and non-technical ones:
people seem to believe that this is the single one existing (and then later
complaining how Google is becoming a gigantic organization touching everything)
while many other companies provide the same service, at 9.9.9.9 or 1.1.1.1,
etc.

> what the helps I asked is that this server (127.0.0.53) returns many 
> timeout during my modperl querying process.

You are not showing specific examples of your timeouts.
And you should have a look at your nameserver logfile.
 
> I think I may ask the sysadmin to add more caching servers and make them 
> have good network connection with internet, am I right?

More instances of recursive nameservers will most probably not help,
but a good network connection surely can only help.

You can use dig with its @ argument to specify which nameserver to query
and then you can compare the reply times.
You may also need to play with the +tcp/+notcp flags to force UDP or TCP
queries and see if things change, and/or the +cd/+nocd flag to enable
or disable DNSSEC processing during troubleshooting.

But all the above is pretty much unrelated to modperl, so offtopic on this
mailing-list I think.

-- 
  Patrick Mevzek