NS record for subzone definition

Chris Thompson cet1 at cam.ac.uk
Tue Mar 13 15:03:38 UTC 2012

On Mar 13 2012, hugo hugoo wrote:

>Thanks for this clear feedback.
>I understand the problem if the subdomain is not on the same name servers
>as the domain. The NS record is needed to could find the subdomain on the
>other name server.
>You said that the NS is not mandatory (it will work fine in the short term)
>in case of the same name server for the domai nand the subdomain. But how
>does it work then if no NS is found?

When asked about "tutu.titi.toto.be", the "be" nameservers give a referral
to the nameservers for "toto.be". When *they* are asked, if they are already
authoritative for the zone "titi.toto.be", they can answer the question
without giving another referral.

But as has been pointed out, such a configuration is horribly fragile. The
set of nameservers (official *and* unofficial) for the zones have to be
the same, and it won't work anyway if the zones are signed, and so on.

One question to ask is: if the set of nameservers for "toto.be" and
"titi.toto.be" are now and for evermore going to be the same, why would
you want to make them separate zones at all? A single zone can have
domain names nested as deep as you like[*] without you needing to make
a zone cut.

[*] subject to the overall limit of 253 characters on the fully
    qualified name

Chris Thompson
Email: cet1 at cam.ac.uk

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