long FQDN resolution

[Matus UHLAR - fantomas]

>On 15.05.25 14:31, DEMBLANS Mathieu wrote:
>>I have a question about mecanism for requests of long subdomains FQDN.
>>Our DNS, which is in recursive configuration, split long fqdn request with subdomains requests like :
>>
>>Original request from the client to our recursive DNS : A a.b.c.d.example.com
>>
>>Requests done by our DNS to the domain example.com NS:
>>A  _.c.d.example.com
>>A _b.c.d.example.com
>>A a.b.c.d.example.com
>>
>>Is it a normal behaviour ?
>>
>>This is only done for 4 levels domains (a.b.example.com for example) and more, not < normal > fqdn (ex : www.example.com).
>>What part of the configuration manage this mecanism ?
>>Is this really usefull ?
>>
>>It is problematic for DNSBL requests because it generate a lot of useless requests and this kind of service look at the number of requests done (usage policy):

On 15.05.25 17:01, Matus UHLAR - fantomas wrote:
>It's been nearly a year since I asked the same, the results are in 
>list archive:
>
>https://lists.isc.org/pipermail/bind-users/2024-May/108537.html

...and the solution was:

turn off QNAME minimisation on DNS servers used by mailservers for 
DNSBL/DNSWL checks.


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