No subject

that our DNS servers had to be listed with ARIN for each of the class C
networks because our upstream ISP doesn't own the entire /16 network, even
though my company was correctly identified on most of the class C network
listing at ARIN.  I contacted our ISP, who submitted the request to ARIN
and cleared up the problem for all of the networks we received from our
(current) ISP.

We also have a class C which we obtained from a former ISP with whom we
are no longer on the best of terms. Reverse DNS lookups remain broken for
this class C, even though the NS records for the class C at that ISP point
to our name servers. (My apologies, but my employer will not allow me to
provide the actual IP in this public forum.)  I understand the lack of a
listing at ARIN for that class C may be the problem.

Question:
I can't determine why the reverse DNS would suddenly stop working.
Can anyone provide a reasonable guess as to why the reverse DNS suddenly
stopped working about 3 weeks ago?
Was there some sort of transition or event which may have occured at ARIN
or elsewhere that flushed a (potentially very) old cache?


I suppose that our normally vocal clients may have just kept quiet until 3
weeks ago, but that seems to be too much of a stretch.
I do not believe that the reverse DNS problem is linked to the Bind
upgrade.  I am currently at a loss to explain the (apparently) sudden
failure of the reverse DNS lookups.

Any help to shed light on this will be greatly appreciated.

Thanks in advance,
Tom