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Peter Turner
Asked: 2009-05-12 07:52:51 +0800 CST

What's the reverse DNS command line utility?

  • 772

What's the command to find the name of a computer given its IP address?

I always forget what this command is, but I know it exists in Windows and I assume it exists on the *nix command-line.

windows linux domain-name-system command-line-interface reverse-dns

13 Answers

  1. Best Answer

    The commands dig and host should be what you're looking for ;)

    On *nix systems, you can use this command:

    dig -x [address]

    Alternatively, you can add +short at the end of the dig command to output only the DNS result.

    There's also nslookup on both *nix and Windows systems for reverse DNS requests.

    • 90

  2. On *nix you can use:

    dig -x [address]
    • 70

  3. Try "host"

    • Forward lookup with host:

      $ host google-public-dns-b.google.com.
google-public-dns-b.google.com has address 8.8.4.4
google-public-dns-b.google.com has IPv6 address 2001:4860:4860::8844

    • Reverse lookup with host:

      $ host 8.8.4.4
4.4.8.8.in-addr.arpa domain name pointer google-public-dns-b.google.com.

    Similar to dig

    • Forward lookup with dig:

      $ dig google-public-dns-b.google.com. +short
8.8.4.4

    • Reverse lookup with dig:

      $ dig -x 8.8.4.4 +short
google-public-dns-b.google.com.

    Try "rdt"

    It takes a little more setup. But if you do this, then you can run this "rdt" PHP script from the command line and it's quite wonderful. It does a few back and forth trips between forward and reverse lookups.

    Download from here: https://github.com/grawity/code/blob/master/net/rdt

    Example. This is what it looks like when it's working:

    $ rdt google-public-dns-b.google.com.
google-public-dns-b.google.com. = 2001:4860:4860::8844, 8.8.4.4
   2001:4860:4860::8844 = dns.google
      dns.google = 2001:4860:4860::8844, 2001:4860:4860::8888, 8.8.4.4, 8.8.8.8
         2001:4860:4860::8888 = dns.google
         8.8.8.8 = dns.google
   8.8.4.4 = dns.google
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  4. On most of the Linux systems that I am aware of you can use:

     nslookup <ip-number EX: 127.0.0.1>

    will work on the command line.

    Come to think of it, isn't nslookup available on Windows XP?

    • 11

  5. This question already has a million answers, but I'm gonna add another one. Here's a little function I wrote for easily doing reverse DNS with dig. Add this to your ~/.bashrc file, reload your shell, and then you can do reverse DNS lookups with revdns 1.2.3.4:

    function revdns() {
    octets=""
    addr="in-addr.arpa"

    # split the IP address into an array of octets
    IFS="." read -r -a octets <<< "$1"

    # add each octet to our $addr string in reverse order
    for octet in "${octets[@]}"; do
         addr=$octet"."$addr
    done

    # run a DNS pointer lookup with dig
    # `+short` makes dig's output very terse (un-verbose)
    # `"${@:2}"` passes any extra params from this command to dig
    dig ptr +short $addr "${@:2}"
}

    Reverse DNS lookups are done by checking the pointer (PTR) records. If you wanna do reverse DNS for "1.2.3.4", you have to lookup pointer records for "4.3.2.1.in-addr.arpa". My function takes in an IP address, reverses the order of the octets (i.e. changes it from 1.2.3.4 to 4.3.2.1), and then uses dig to execute the PTR lookup I just described.

    You can, of course, just use nslookup 1.2.3.4 if you have it, but I prefer this dig-based solution because it uses the OS' DNS servers instead of nslookup-provided ones (if you want, by the way, you can add additional dig flags when you call revdns, and they will get passed to dig)

    • 4

  6. I'm well aware that dig/host/nslookup are the standard tools for these, but I keep these around for testing the OS's resolution (essentially, to test nsswitch.conf is working correctly):

    gethostbyname:

    #!/usr/bin/perl

use Socket;

my @t = gethostbyname($ARGV[0]);
print "\$name     = $t[0]\n"; shift(@t);
print "\$aliases  = $t[0]\n"; shift(@t);
print "\$addrtype = $t[0]\n"; shift(@t);
print "\$length   = $t[0]\n"; shift(@t);

foreach (@t) {
  print "          = ", inet_ntoa($_), "\n";
}

    gethostbyaddr:

    #!/usr/bin/perl

use Socket;

my @t = gethostbyaddr(inet_aton($ARGV[0]), AF_INET);
print "\$name     = $t[0]\n"; shift(@t);
print "\$aliases  = $t[0]\n"; shift(@t);
print "\$addrtype = $t[0]\n"; shift(@t);
print "\$length   = $t[0]\n"; shift(@t);

foreach (@t) {
  print "          = ", inet_ntoa($_), "\n";
}

    example:

    g3 0 /home/jj33/swap > gethostbyname www.google.com
$name     = www.l.google.com
$aliases  = www.google.com
$addrtype = 2
$length   = 4
          = 72.14.205.147
          = 72.14.205.103
          = 72.14.205.104
          = 72.14.205.99
g3 0 /home/jj33/swap > gethostbyaddr 72.14.205.147 
$name     = qb-in-f147.google.com
$aliases  = 
$addrtype = 2
$length   = 4
          = 72.14.205.147
    • 3

  7. On Windows I got in to the habit of using:

    ping -a <ip address>

    as this will also reflect data from your hosts file and WINS and so on.

    • 3

  8. If you're using nslookup it's this (assuming 192.168.0.1 as the IP in question)

    > set type=ptr
> 1.0.168.192.in-addr.arpa

    EDIT: Remember a reverse lookup only works if there is a PTR record created for the IP, and it's not guaranteed to return the hostname you're looking for. Completely depends on how DNS is configured and maintained in your situation.

    • 1

  9. Powershell:

    [net.dns]::gethostentry("69.59.196.212").HostName
    • 1

  10. I prefer the command-line dig for Windows (available here: http://members.shaw.ca/nicholas.fong/dig/) to nslookup any day.

    If you have to test/administer DNS from a Windows workstation, grab this tool. Then:

    C:\dig>dig -x <IP Address>

    ...also, remember to add c:\dig to your path!

    • 1