Strange DNS issue

[Alexander H.]

We are dealing with a rather strange DNS issue and I am hoping somebody
will be able to assist us with understanding.

Via DHCP we are allocated two DNS servers











*resolvectl Global         Protocols: -LLMNR -mDNS -DNSOverTLS
DNSSEC=no/unsupported  resolv.conf mode: stubLink 2 (eth0)    Current
Scopes: DNS         Protocols: +DefaultRoute -LLMNR -mDNS -DNSOverTLS
DNSSEC=no/unsupportedCurrent DNS Server: 10.1.1.1       DNS Servers:
10.1.1.1 10.1.1.2        DNS Domain: reddog.**domain*



*.localLink 3 (enP28932s1)    Current Scopes: none         Protocols:
-DefaultRoute -LLMNR -mDNS -DNSOverTLS DNSSEC=no/unsupported*

The reverse lookup completes successfully

*dig -x 10.1.1.1* and *dig -x 10.1.1.2* both correctly resolve to the DNS
server's hostnames

However the forward lookup fails

*dig dnsserver1.domain.local -> Fails*
*dig dnsserver2.domain.local -> **Fails*

However with specifying the DNS server explicitly the requests complete
successfully

*dig @**10.1.1.1 **dnsserver1.domain.local -> **Works*
*dig @**10.1.1.1 **dnsserver2.domain.local -> **Works*
*dig @**10.1.1.2 **dnsserver1.domain.local -> **Works*
*dig @**10.1.1.2 **dnsserver2.domain.local -> Works*

I don't understand why it works when we set the DNS server and fails when
using the default system DNS servers.

Kind regards
Alex
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