conflicting subdomain delegation

[Frank Liu]

Thanks for confirming bind behavior matches what I saw.
I noticed other resolvers (eg: @8.8.8.8) works differently, c.b.a.com NS
host2 actually got used, not ignored as occluded data.
Is this a bind specific implementation, not required by any RFCs?
>From authoritative dns perspective, Amazon Route53 allows you to add both
delegations in the a.com zone without any "out of zone data" error.


On Tue, Nov 13, 2018 at 1:50 PM Mark Andrews <marka at isc.org> wrote:

>
> > On 14 Nov 2018, at 4:04 am, Frank Liu <gfrankliu at gmail.com> 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, there are two NS delegations
>
> This one is used.
>
> > b.a.com NS host1
>
> This one is ignored as it is occluded data.
>
> > c.b.a.com NS host2
> >
> > On host1 in zone b.a.com, there is
> > c.b.a.com NS host3
>
> Which is occluded data or glue depending upon the rest of the contents of
> the zone.
>
> > As you can see, there is a conflicting delegation for c.b.a.com. If I
> look a name 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).
>
> dig +trace follows the returned delegations.
>
> > Any ideas?
> > Thanks!
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> --
> Mark Andrews, ISC
> 1 Seymour St., Dundas Valley, NSW 2117, Australia
> PHONE: +61 2 9871 4742              INTERNET: marka at isc.org
>
>
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