I was beaten to it! It's called QNAME minimisation and is specified here: https://datatracker.ietf.org/doc/html/rfc9156
In BIND it can be disabled with this statement: https://bind9.readthedocs.io/en/v9.20.8/reference.html#namedconf-statement-qname-minimization Hope that helps, Greg On Thu, 15 May 2025 at 15:32, DEMBLANS Mathieu <demblan...@mipih.fr> wrote: > Hello, > > 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 <http://a.b.c.d.example.com>* > > > > Requests done by our DNS to the domain example.com NS: > > *A _.c.d.example.com <http://c.d.example.com>* > > *A _b.c.d.example.com <http://b.c.d.example.com>* > > *A a.b.c.d.example.com <http://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): > > > > > > > > > > > -- > Visit https://lists.isc.org/mailman/listinfo/bind-users to unsubscribe > from this list > > ISC funds the development of this software with paid support > subscriptions. Contact us at https://www.isc.org/contact/ for more > information. > > > bind-users mailing list > bind-users@lists.isc.org > https://lists.isc.org/mailman/listinfo/bind-users >
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