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

[Reindl Harald]

Am 16.12.19 um 20:13 schrieb Roberto Carna:
> I have a primary and a secondary BIND9 DNS servers, working as master /
> slave with zone transfers between them.
> 
> 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:
> 
> 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 ? Because I expect only DNS traffic going to
> DNS1 because it is before DNS2 in /etc/resolv.conf

it's not unusual behavior these days that a client asks both nameservers
and takes the answer of the faster one

that avoid large delays in case of timeouts when the asked one is down