DNS queries go to primary and secondary DNS servers at the same time

[Roberto Carna]

OK, thanks a lot for your comments.

I'll investigate this topic.

Greetings !!!

El mar., 17 dic. 2019 a las 14:42, Chuck Aurora (<ca at nodns4.us>) escribió:

> On 2019-12-16 13:13, Roberto Carna wrote:
> > I have a primary and a secondary BIND9 DNS servers, working as master
> > / slave with zone transfers between them.
>
> Primary/master and secondary/slave are concepts which apply only to
> authoritative servers, and in this case you are talking about these
> servers acting as resolvers, not authoritative.
>
> > I have several Linux machines (desktops and servers) with Debian and
> > Mint.
> >
> > I've realized, using TCPDUMP at DNS1 and DNS2, that all DNS queries
> > from Linux machines go to both DNS1 and DNS2 BIND servers at the same
> > time.
> >
> > In all Linux machines we have setup the DNS resolution using
> > /etc/resolv.conf:
>
> And resolv.conf is not an ISC BIND thing.  In GNU/Linux it's usually
> GNU glibc which uses that file.
>
> > nameserver IP_dns1
> > nameserver IP_dns2
> >
> > But when the from Linux clients I execute:
> >
> > $ host <some_fqdn>
> >
> > I can see UDP traffic arriving to DNS1 and DNS2 at the same time.
> >
> > What can be the problem ?
>
> I'm not sure I would see that as a problem, although you might want to
> simplify and use only a single resolver IP address.  If your site is
> big enough to need two or more resolvers, use an anycast address.  For
> example, Google's 8.8.8.8 is a large farm of nameservers distributed
> throughout the world.
>
> > Because I expect only DNS traffic going to
> > DNS1 because it is before DNS2 in /etc/resolv.conf.
>
> GNU glibc does have documentation, starting with the resolv.conf(5)
> manual.  I'm not sure if there is a specific mailing list or forum to
> discuss it, however.
> _______________________________________________
> Please visit https://lists.isc.org/mailman/listinfo/bind-users to
> unsubscribe from this list
>
> bind-users mailing list
> bind-users at lists.isc.org
> https://lists.isc.org/mailman/listinfo/bind-users
>
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <https://lists.isc.org/pipermail/bind-users/attachments/20191218/7d95a183/attachment.htm>