mysterious failures/wrong-answers in reverse DNS lookup

[Jeremy C. Reed]

On Wed, 23 Jul 2025, Michael Richardson wrote:

> When I ask from the IETF123 network:
>
> ;; SERVER: 31.130.231.0#53(31.130.231.0) (UDP)
> ;; ANSWER SECTION:
> d.0.0.f.e.b.a.b.0.0.0.0.0.0.0.0.0.0.0.0.f.0.0.0.0.b.0.f.7.0.6.2.ip6.arpa. 7200 IN PTR nic.sandelman.ca.
>
> which is entirely correct.

Probably 31.130.231.0 got the answer from @sns.cooperix.net. (instead of 
@nic.sandelman.ca.)

...

nic.sandelman.ca.
is also authoritatively serving:

0.0.0.0.0.0.0.0.0.0.0.0.f.0.0.0.0.b.0.f.7.0.6.2.ip6.arpa. 86400 IN SOA . 
. 0 28800 7200 604800 86400
0.0.0.0.0.0.0.0.0.0.0.0.f.0.0.0.0.b.0.f.7.0.6.2.ip6.arpa. 0 IN NS .

That may give you a clue.

You may have two zones serving the same.