conflicting subdomain delegation

[Mark Andrews]

> 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