[ About | Licence | Contacts ]
Written by Oleksandr Gavenko (AKA gavenkoa), compiled on 2017-01-30 from rev ccaa2f364422+.

DNS.

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 @8.8.4.4 +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 8.8.8.8

$ dig @8.8.8.8 A defun.work
$ dig +nocmd +noall +answer defun.work

Host name from IP.

If that information available:

$ nslookup -type=ptr 8.8.8.8

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
...
;; ANSWER SECTION:
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       195.64.190.1
adm.dp.gov.ua.          3600    IN      A       195.64.190.1

Get info about NS.

Version of running NS:

$ dig @4.2.2.1 version.bind chaos txt
$ nslookup -q=txt -class=CHAOS version.bind. 4.2.2.1

Server name:

$ dig @4.2.2.1 id.server txt chaos
$ nslookup -q=txt -class=CHAOS id.server. 4.2.2.1

$ dig @4.2.2.1 hostname.bind txt chaos
$ nslookup -q=txt -class=CHAOS hostname.bind. 4.2.2.1

That strings come from BIND config:

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

How reread config file?

FreeBSD:

$ named.reload