[plug] Strange DNS issue

[Paul Dean]

What does `host dnsserver1.domain.local` produce?
Also has nsswitch.conf been changed in the host in question?
What has been set in your /etc/hosts file?

---
Thanks

Paul Dean.

"Life is not WHAT you make it, it's WHO you have in it..."

On 2025-12-08 20:53, alex via plug wrote:
> Just why does it work when I specify the DNS servers explicitly,  but
> not without it ?
> 
> -------- Original message --------
> From: Onno Benschop via plug <plug at plug.org.au>
> Date: 8/12/25 16:52 (GMT+08:00)
> To: PLUG mailing list <plug at plug.org.au>
> Subject: Re: [plug] Strange DNS issue
> 
> Your DNS domain appears to be reddog.domain.local, rather than
> domain.local
> 
> --
> finger painting on glass is an inexact art - apologies for any errors
> in this scra^Hibble
> 
> ()/)/)() ..ASCII for Onno..
> 
> On Mon, 8 Dec 2025, 16:01 Alex H. via plug, <plug at plug.org.au> wrote:
> 
>> 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: stub
>> 
>> Link 2 (eth0)
>> Current Scopes: DNS
>> Protocols: +DefaultRoute -LLMNR -mDNS -DNSOverTLS
>> DNSSEC=no/unsupported
>> Current DNS Server: 10.1.1.1
>> DNS Servers: 10.1.1.1 10.1.1.2
>> DNS Domain: reddog.domain.local
>> 
>> Link 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 [1] dnsserver1.domain.local -> Works
>> 
>> dig @10.1.1.1 [1] dnsserver2.domain.local -> Works
>> 
>> dig @10.1.1.2 [2] dnsserver1.domain.local -> Works
>> 
>> dig @10.1.1.2 [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_______________________________________________
>> PLUG discussion list: plug at plug.org.au
>> https://lists.plug.org.au/mailman/listinfo/plug
>> Committee e-mail: committee at plug.org.au
>> PLUG Membership: http://www.plug.org.au/membership
> 
> 
> Links:
> ------
> [1] http://10.1.1.1
> [2] http://10.1.1.2
> _______________________________________________
> PLUG discussion list: plug at plug.org.au
> https://lists.plug.org.au/mailman/listinfo/plug
> Committee e-mail: committee at plug.org.au
> PLUG Membership: http://www.plug.org.au/membership