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Written by Oleksandr Gavenko (AKA gavenkoa), compiled on 2024-04-01 from rev 052223c22317.


About DNS resolving protocol

Default port for name resolving is 53:

$ nslookup -port=53 microsoft.com

Debugging name resolution

$ nslookup -debug microsoft.com

Dumping all available resords:

$ nslookup -type=any microsoft.com

Timing information and traces available via:

$ dig +trace google.com
$ dig @ +noall +answer +stats A defun.work

Despite dig shown only names for NS replays also have IP adresses (to avoid chicken/egg ptoblem when you request name resolution but asked to resolve another name). To see IP addressed use +additional option:

$ dig +trace +additional google.com

IP from host name

This request is for the A record and default for nslookup command:

$ nslookup defun.work
$ nslookup -type=a defun.work
$ nslookup -type=a defun.work

$ dig @ A defun.work
$ dig +nocmd +noall +answer defun.work

Host name from IP

If that information available:

$ nslookup -type=ptr
$ dig @ -x

$ dig +noall +answer @ PTR   21599   IN      PTR     google-public-dns-b.google.com.

$ host domain name pointer google-public-dns-b.google.com.

List authoritative NS for domain

$ dig ns defun.work
$ nslookup -type=ns defun.work

List MX records for domain

$ dig mx mail.google.com
$ nslookup -type=mx mail.google.com

Query for TXT records

$ dig -t TXT google.com
$ dig google.com TXT
$ nslookup -type=txt google.com
$ nslookup -q=txt google.com
$ host -t txt google.com

List SOA records for domain

SOA ("Start Of Authority") Record for a domain provides technical information about the domain:

$ dig soa defun.work

Human readable format can be viewed via:

$ nslookup -type=mx defun.work

  origin = ns1.mindsandmachines.com
  mail addr = admin.mindsandmachines.com
  serial = 2011091101
  refresh = 10800
  retry = 7200
  expire = 604800
  minimum = 86400

Email adress for domain administrator is admin@mindsandmachines.com for above output.

List domain names

$ dig ns dp.gov.ua
dp.gov.ua.              3600    IN      NS      ns.giknpc.com.ua.

$ dig @ns.giknpc.com.ua dp.gov.ua AXFR
dp.gov.ua.              3600    IN      MX      200 relay2.giknpc.com.ua.
dp.gov.ua.              3600    IN      A
adm.dp.gov.ua.          3600    IN      A

Get info about NS

Version of running NS:

$ dig @ version.bind chaos txt
$ nslookup -q=txt -class=CHAOS version.bind.

Server name:

$ dig @ id.server txt chaos
$ nslookup -q=txt -class=CHAOS id.server.

$ dig @ hostname.bind txt chaos
$ nslookup -q=txt -class=CHAOS hostname.bind.

That strings come from BIND config:

options {
  version "none of your business";
  server-id "Host A";
  hostname "Host A";

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How reread config file?


$ named.reload

Windows built-in DNS server

Built-in DNS server respects hosts file located %WINDIR%\system32\drivers\etc\hosts.

Show DNS cache:

ipconfig /displaydns

Flush the cache content:

ipconfig /flushdns

Refreshes all DHCP leases and re-registers DNS names:

ipconfig /registerdns