I am a new Linux and Unix command line user. How do I test or check reverse DNS for given IP address under Linux, OS X, BSD, Unix-like or Windows XP/Server 2003 based systems?
Reverse DNS lookup (also known as rDNS) is a process to determine the hostname associated with a given IP address.
Typically, the DNS is used to determine what IP address is associated with a given hostname; so to reverse resolve a known IP address is to lookup what the associated hostname for it. A reverse lookup is often referred to simply as reverse resolving, or more specifically reverse DNS lookups.
[donotprint][/donotprint]The most common uses of the reverse DNS are:
- Anti-spam
- Network troubleshooting
- Avoid spammers and phishers using a forward confirmed reverse DNS etc
You can use standard UNIX / Linux utilities such as nslookup command, dig command or host command to find out reverse DNS of a given IP address.
Task: Find Reverse DNS for IP 75.126.43.235 under Linux/UNIX
Type the following host command:
$ host ip-address-here
$ host 75.126.43.235
Sample outputs:
235.43.126.75.in-addr.arpa domain name pointer cyberciti.org.
In this example output, IP 75.126.43.235 is reverse mapped to cyberciti.org. Here is another reverse lookups done using dig command:
$ dig -x ip-address-here
$ dig -x 75.126.153.206
Sample outputs:
; <<>> DiG 9.8.3-P1 <<>> -x 75.126.153.206
;; global options: +cmd
;; Got answer:
;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 39113
;; flags: qr rd ra; QUERY: 1, ANSWER: 1, AUTHORITY: 0, ADDITIONAL: 0
;; QUESTION SECTION:
;206.153.126.75.in-addr.arpa. IN PTR
;; ANSWER SECTION:
206.153.126.75.in-addr.arpa. 20975 IN PTR satohost.com.
;; Query time: 32 msec
;; SERVER: 8.8.8.8#53(8.8.8.8)
;; WHEN: Sat Feb 8 04:40:28 2014
;; MSG SIZE rcvd: 76
Hiding additional display info while doing reverse ip lookup using dig command
You can only display the answer section of a reply with +answer option and clear all other display info with +noall option as follow:
dig +noall +answer -x 75.126.153.206 |
Sample outputs:
206.153.126.75.in-addr.arpa. 80127 IN PTR satohost.com.
Task: Find Reverse DNS for IP 75.126.43.235 under Linux/UNIX/Windows
nslookup works under Windows and UNIX like oses:
nslookup ip-address-here
nslookup 75.126.43.235
Output:
Server: 208.67.222.222 Address: 208.67.222.222#53 Non-authoritative answer: 235.43.126.75.in-addr.arpa name = cyberciti.org. Authoritative answers can be found from:
Demo: Reverse IP lookup on Linux, Unix, OS X and MS-Windows
