Reverse DNS Lookup

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Template:Networking In computer networking, reverse DNS lookup or reverse DNS resolution (rDNS) is the determination of a domain name that is associated with a given IP address using the Domain Name System (DNS) of the Internet. To look up the DNS record for your server, use the nslookup or host commands. Substitute your own email server information in the example.

Windows
Type nslookup Server IP Address into the command prompt and hit Enter (eg., nslookup 131.128.1.1)
Macintosh
Type host or nslookup Server IP Address into Terminal and hit Enter (eg., host 131.128.1.1)

Successful Reverse DNS Lookup

Windows
C:\Users\Username>nslookup 131.128.1.1
Server: bigbluebug.uri.edu
Address: 131.128.1.126

Name: uriacc.uri.edu
Address: 131.128.1.1


Macintosh

Terminal:~ user$ host 131.128.1.1
1.1.128.131.in-addr.arpa domain name pointer uriacc.uri.edu.

Terminal:~ user$ nslookup 131.128.1.1
Server: 131.128.1.126
Address: 131.128.1.126#53

1.1.128.131.in-addr.arpa name = uriacc.uri.edu.


Unsuccessful Reverse DNS Lookup

Windows
C:\Users\Username>nslookup 131.128.1.1
Server: bigbluebug.uri.edu
Address: 131.128.1.126

***bigbluebug.uri.edu can't find 131.128.1.251: Non-existent domain

Macintosh
Terminal:~ user$ host 131.128.1.251
Host 251.1.128.131.in-addr.arpa not found: 3(NXDOMAIN)

Terminal:~ user$ nslookup 131.128.1.251
Server: 131.128.1.126
Address: 131.128.1.126#53

**server can't find 251.1.128.131.in-addr.arpa: NXDOMAIN


If you need additional DNS records for your server(s), contact your Internet Service Provider. Call the ITS Help Desk at 401-874-HELP (4357) if you have questions or are not sure what to do.