: About Nslookup Results When I try to resolve 113.181.205.189 and 203.148.85.74, I get localhost. and HM-DC-BS-BIG. results: nslookup 113.181.205.189 Non-authoritative answer: 189.205.181.113.in-addr.arpa

@LarsenBagley505

In DNS, domain registrants and their registrars have authority over A records that resolve domain names to IP addresses. If you register a domain, you get to pick the IP address it resolves to.

On the other hand, IP address blocks are assigned to ISPs that connect machines to the Internet. The PTR records are in special "in-addr.arpa." DNS zones corresponding to the IP address blocks assigned to ISPs. Thus, the ISPs have authority over the rDNS zones. And so, to add those PTR records, you usually need to consult with an ISP, or have the ability to do dynamic DNS updates on the zones. The latter would usually be because the ISP has an insecure DNS server infrastructure.

When an ISP assigns a device an IP address, they usually also add a corresponding PTR record with some geographic information in the data. This allows them to correlate things in their logs easier.

Having rDNS set up also makes flaky software work much faster, when said software tries to log the hostname of a machine when it otherwise would not have one. Without the entry, the software usually times out on DNS after a few seconds, and that feels like the Internet is slow.

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@Jamie184

Use whois ipaddress instead.

113.181.205.189

% Information related to '113.181.0.0 - 113.181.255.255'

inetnum: 113.181.0.0 - 113.181.255.255
netname: VNPT-VNNIC-VN
descr: VietNam Post and Telecom Corporation
descr: FTTH Service
country: VN
admin-c: NXC1-AP
tech-c: KNH1-AP
status: ALLOCATED NON-PORTABLE
mnt-by: MAINT-VN-VNPT
mnt-irt: IRT-VNNIC-AP
changed: hm-changed@vnnic.net.vn 20141128
source: APNIC

irt: IRT-VNNIC-AP
address: Ha Noi, VietNam
phone: +84-4-35564944
fax-no: +84-4-37821462
e-mail: hm-changed@vnnic.net.vn
abuse-mailbox: hm-changed@vnnic.net.vn
admin-c: PT174-AP
tech-c: NTTT1-AP
auth: # Filtered
mnt-by: MAINT-VN-VNNIC
changed: hm-changed@vnnic.net.vn 20101108
source: APNIC

person: Khanh Nguyen Hien
nic-hdl: KNH1-AP
e-mail: hathm@vdc.com.vn
address: Vietnam Datacommunications Company (VDC)
address: Lo IIA Lang Quoc te Thang Long, Cau Giay, Ha Noi
phone: +84-4-3793 0563
fax-no: +84-4-32811506
country: VN
changed: hm-changed@vnnic.net.vn 20090227
mnt-by: VNPT
source: APNIC

person: Nguyen Xuan Cuong
nic-hdl: NXC1-AP
e-mail: cuongnx@vnpt.com.vn
address: Vietnam Posts and Telecommunications (VNPT)
address: 57 Huynh Thuc Khang
address: Hanoi, Vietnam
phone: +84-4-37741236
fax-no: +84-4-37741205
country: VN
changed: hm-changed@vnnic.net.vn 20090922
mnt-by: MAINT-VN-VNPT
source: APNIC


203.148.85.74

% Information related to '203.148.84.0 - 203.148.85.255'

inetnum: 203.148.84.0 - 203.148.85.255
netname: INDOTRANS-ID
descr: PT. Indotrans Data
descr: Internet Service Provider
descr: Gedung Annex lantai dasar, Komplek YTKI
descr: Jln. Jend. Gatot Subroto No. 44
descr: Jakarta 12710
country: ID
admin-c: DC1015-AP
tech-c: DC1015-AP
remarks: Send Spam& Abuse report to: noc@indotrans.net.id
status: ALLOCATED PORTABLE
mnt-by: MNT-APJII-ID
mnt-routes: MAINT-ID-INDOTRANS
mnt-irt: IRT-INDOTRANS-ID
changed: hostmaster@idnic.net 20130502
changed: hostmaster@idnic.net 20130906
mnt-lower: MAINT-ID-INDOTRANS
source: APNIC

irt: IRT-INDOTRANS-ID
address: PT. Indotrans Data
address: Gedung Raudha Lt. 2 Blok B.3
address: Jl. Terusan Kuningan H.R Rasuna Said No. 21
address: Jakarta, 12710
e-mail: noc@indotransdata.net
abuse-mailbox: noc@indotransdata.net
admin-c: DC1015-AP
tech-c: DC1015-AP
auth: # Filtered
mnt-by: MAINT-ID-INDOTRANS
changed: noc@indotransdata.net 20110329
changed: hostmaster@idnic.net 20110329
source: APNIC

person: Dwi Cahyoko
nic-hdl: DC1015-AP
e-mail: dwi@indotrans.net.id
address: Perumahan Bumi Sentosa blok A6 No: 18
address: RT 08 RW 09, Bogor
phone: +62-21-68007806
fax-no: +62-21-5279906
country: ID
changed: hostmaster@idnic.net 20080923
changed: hostmaster@idnic.net 20130906
mnt-by: MAINT-ID-INDOTRANS
source: APNIC

% Information related to '203.148.84.0/23AS45289'

route: 203.148.84.0/23
descr: Route Object of PT Indotrans Data
descr: Internet Service Provider
descr: Gedung Annex Lt.Dasar
descr: Jl. Jendral Gatot Subroto No.44
descr: Jakarta 12710
country: ID
origin: AS45289
mnt-by: MAINT-ID-INDOTRANS
changed: hostmaster@idnic.net 20140430
source: APNIC

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@Pope3001725

Those are the results of doing a reverse DNS (RDNS) lookup using the IP PTR records.

You can think of the PTR record as an opposite of the A record. While the A record points a domain name to an IP address, the PTR record resolves the IP address to a domain/hostname. PTR records are used for reverse DNS lookups.


Reverse DNS lookups for IPv4 addresses use a reverse IN-ADDR entry in
the special domain in-addr.arpa. In this domain, an IPv4 address is
represented as a concatenated sequence of four decimal numbers,
separated by dots, to which is appended the second level domain suffix
.in-addr.arpa. The four decimal numbers are obtained by splitting the
32-bit IPv4 address into four 8-bit portions and converting each 8-bit
portion into a decimal number. These decimal numbers are then
concatenated in the order: least significant 8-bit portion first
(leftmost), most significant 8-bit portion last (rightmost). It is
important to note that this is the reverse order to the usual
dotted-decimal convention for writing IPv4 addresses in textual form.


RDNS in Wikipedia

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