conflicting subdomain delegation

[Lyle Giese]

On 11/13/2018 11:04 AM, Frank Liu wrote:
> Hi,
>
> Is there a RFC determining which nameserver to use if there is a 
> conflicting subdomain delegation?
>
> eg:
> In the zone of a.com <http://a.com>, there are two NS delegations:
>
> b.a.com <http://b.a.com> NS host1
> c.b.a.com <http://c.b.a.com> NS host2
>
> On host1 in zone b.a.com <http://b.a.com>, there is
> c.b.a.com <http://c.b.a.com> NS host3
>
> As you can see, there is a conflicting delegation for c.b.a.com 
> <http://c.b.a.com>. If I look a name d.c.b.a.com <http://d.c.b.a.com>, 
> will the nameserver host2 or host3 be used?
> dig +trace seems to go to host2, but bind9 as a resolver goes to host3.
> (the test was done on a centos7).
>
> Any ideas?
> Thanks!
>
>
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I would expect that behavior if the Bind9 resolver was setup to query 
host1.  If bind9 queries a server that is authoritive for b.a.com, I 
would expect that result.  If the bind9 resolver is setup to query a 
recursive only server(other than host1), I would expect the same 
behavior as the +trace result.

so I think the answer is dependant on how your bind9 resolver is configured.

Lyle Giese

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