Origin of reverse lookup

Reindl Harald h.reindl at thelounge.net
Sat Jun 19 10:36:51 UTC 2021

Am 19.06.21 um 12:10 schrieb alcol alcol:
> ISP Have is a normale DNS zone as forward ones
> they does not offer remote mainteining as you should own all subnet 
> class and are directly downloaded from iana if I remember well.

ptr zones are the same way delegated as any other zones

> if something go wrong with the zone ISP will have issue from tld.


> in past I had a master reverse lookup maintained from me downloaded from 
> isp becous iana can't go around the world to download and to avoid 
> issues in download.

dns zones are not downloaded

> as are zones with so few changes isp could allow something like a 
> cpannel to change some records.

that don't scale given that most customers just have a single IP

in case you have a /24 the ISP can delegate the whole zone to you, look 
at the authoritative nameservers below

[harry at srv-rhsoft:/downloads]$ dig -x

; <<>> DiG 9.11.32-RedHat-9.11.32-1.fc33 <<>> -x
;; global options: +cmd
;; Got answer:
;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 21949
;; flags: qr rd ra; QUERY: 1, ANSWER: 1, AUTHORITY: 2, ADDITIONAL: 3

; EDNS: version: 0, flags:; udp: 1024
; COOKIE: 68fa6f61a7537e2c684ca5d260cdc67126f45c0615547511 (good)
;      IN      PTR

;; ANSWER SECTION: 7200  IN      PTR     arrakis.thelounge.net.

73.118.91.in-addr.arpa. 7200    IN      NS      ns1.thelounge.net.
73.118.91.in-addr.arpa. 7200    IN      NS      ns2.thelounge.net.

ns2.thelounge.net.      7200    IN      A       91.118.73.
ns1.thelounge.net.      7200    IN      A

> usually reverse lookup are resolved with a standard naming with ip and 
> isp name

for consumer ranges: yes

> if you run a mail server could be usefull 

if you run a mailserver it is a must, at least when you care to deliver 
your mails, as well make sure your HELO-hostname matches too

many sites add at least points to the sapm scoring for clients like that:

warning: hostname szkoleniagospodarka.pl does not resolve to address Name or service not known

> if not a reverse lookup is not 
> so much used

well, in case of servers i prefer PTR/A matching no matter if it is 
supposed to send mail and the same goes for internal networks i maintain

> ------------------------------------------------------------------------
> *From:* bind-users <bind-users-bounces at lists.isc.org> on behalf of 
> techlists at phpcoderusa.com <techlists at phpcoderusa.com>
> *Sent:* Saturday, June 19, 2021 1:17 AM
> *To:* bind-users at lists.isc.org <bind-users at lists.isc.org>
> *Subject:* Origin of reverse lookup
> Hi,
> I had my ISP configure a reverse lookup years ago.  They say they no
> longer offer that service and there is no reverse lookup for my IP.
> I keep running into this old reverse lookup and do not know where it is
> coming from.
> When I run https://intodns.com/ <https://intodns.com/> it shows this 
> reverse lookup and not the
> one I just configured on my local box.
> Any thoughts on how I might resolve this or find who is hosting this
> reverse lookup?
> Thanks!!

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