Network Command Quick Book 🌐 •

BASICS

Common DNS record types

A maps a domain name to an IPv4 address.
AAAA maps a domain name to an IPv6 address.
MX tells email where to go for a domain.
NS shows the authoritative nameservers for a domain.
SOA stores primary zone information like the main nameserver and DNS timing values.
TXT stores free-form text, often used for SPF, DKIM, and verification tokens.
PTR is used for reverse DNS, mapping an IP address back to a hostname.

Quick examples

A → example.com → 93.184.216.34
AAAA → example.com → 2606:2800:220:1:248:1893:25c8:1946
MX → gmail.com → gmail-smtp-in.l.google.com
NS → example.com → a.iana-servers.net
TXT → example.com → "v=spf1 -all"

BASIC LOOKUP

Query the default `A` record for a domain

dig example.com

Example output:

; <<>> DiG 9.10.6 <<>> example.com
;; QUESTION SECTION:
;example.com.                  IN      A

;; ANSWER SECTION:
example.com.           300     IN      A       93.184.216.34

;; Query time: 24 msec
;; SERVER: 192.168.1.1#53(192.168.1.1)

RECORD TYPES

Query an `A` record explicitly

dig example.com A

Example output:

;; ANSWER SECTION:
example.com.           300     IN      A       93.184.216.34

Query an `AAAA` record for IPv6

dig example.com AAAA

Example output:

;; ANSWER SECTION:
example.com.           300     IN      AAAA    2606:2800:220:1:248:1893:25c8:1946

Query mail exchange records

dig gmail.com MX

Example output:

;; ANSWER SECTION:
gmail.com.             300     IN      MX      5 gmail-smtp-in.l.google.com.
gmail.com.             300     IN      MX      10 alt1.gmail-smtp-in.l.google.com.

Query nameserver records

dig example.com NS

Example output:

;; ANSWER SECTION:
example.com.           172800  IN      NS      a.iana-servers.net.
example.com.           172800  IN      NS      b.iana-servers.net.

Query the start of authority record

dig example.com SOA

Example output:

;; ANSWER SECTION:
example.com.           3600    IN      SOA     ns.icann.org. noc.dns.icann.org. 2025010101 7200 3600 1209600 3600

Query TXT records

dig example.com TXT

Example output:

;; ANSWER SECTION:
example.com.           300     IN      TXT     "v=spf1 -all"

SHORT OUTPUT

Show only the answer section

dig example.com +short

Example output:

93.184.216.34

Show only short MX answers

dig gmail.com MX +short

Example output:

5 gmail-smtp-in.l.google.com.
10 alt1.gmail-smtp-in.l.google.com.
20 alt2.gmail-smtp-in.l.google.com.

USING A SPECIFIC DNS SERVER

Ask Google Public DNS directly

dig @8.8.8.8 example.com

Example output:

;; SERVER: 8.8.8.8#53(8.8.8.8)

;; ANSWER SECTION:
example.com.           300     IN      A       93.184.216.34

Ask Cloudflare DNS directly

dig @1.1.1.1 example.com AAAA

Example output:

;; SERVER: 1.1.1.1#53(1.1.1.1)

;; ANSWER SECTION:
example.com.           300     IN      AAAA    2606:2800:220:1:248:1893:25c8:1946

REVERSE LOOKUP

Resolve an IP address back to a host name

dig -x 8.8.8.8

Example output:

;; ANSWER SECTION:
8.8.8.8.in-addr.arpa.  1800    IN      PTR     dns.google.

TRACE DNS RESOLUTION

Trace the full resolution path from the root servers

dig example.com +trace

Example output:

.                       518400  IN      NS      a.root-servers.net.
com.                    172800  IN      NS      a.gtld-servers.net.
example.com.            172800  IN      NS      a.iana-servers.net.
example.com.            300     IN      A       93.184.216.34

CHECK ALL SECTIONS

Display answer, authority, and additional sections clearly

dig example.com +noall +answer +authority +additional

Example output:

example.com.           300     IN      A       93.184.216.34
a.iana-servers.net.    172800  IN      A       199.43.135.53
b.iana-servers.net.    172800  IN      A       199.43.133.53

COMMON FLAGS

Skip comments and show only records

dig example.com +nocmd +noquestion +nocomments +nostats

Example output:

example.com.           300     IN      A       93.184.216.34

dig example.com +dnssec

Example output:

;; flags: qr rd ra ad; QUERY: 1, ANSWER: 2, AUTHORITY: 0, ADDITIONAL: 1

PRACTICAL CHECKS

Verify a website points to the expected IP

dig myapp.example.com +short

Example output:

203.0.113.10

Verify a domain has mail routing configured

dig myapp.example.com MX +short

Example output:

10 mail.myapp.example.com.

Verify a TXT record such as SPF or domain verification

dig myapp.example.com TXT +short

Example output:

"v=spf1 include:_spf.example.net ~all"

NSLOOKUP EXAMPLES

Use `nslookup` for a basic lookup

nslookup example.com

Example output:

Server:  192.168.1.1
Address: 192.168.1.1#53

Non-authoritative answer:
Name:    example.com
Address: 93.184.216.34

Query a specific record type

nslookup -type=MX gmail.com

Example output:

gmail.com  mail exchanger = 5 gmail-smtp-in.l.google.com.
gmail.com  mail exchanger = 10 alt1.gmail-smtp-in.l.google.com.

Query using a specific DNS server

nslookup example.com 8.8.8.8

Example output:

Server:  8.8.8.8
Address: 8.8.8.8#53

Non-authoritative answer:
Name:    example.com
Address: 93.184.216.34

HOST EXAMPLES

Use `host` for a basic lookup

host example.com

Example output:

example.com has address 93.184.216.34
example.com has IPv6 address 2606:2800:220:1:248:1893:25c8:1946

Use `host` for MX records

host -t MX gmail.com

Example output:

gmail.com mail is handled by 5 gmail-smtp-in.l.google.com.
gmail.com mail is handled by 10 alt1.gmail-smtp-in.l.google.com.

Reverse lookup an IP address

host 8.8.8.8

Example output:

8.8.8.8.in-addr.arpa domain name pointer dns.google.

See which DNS server answered you

With dig:

dig example.com

Look for:

;; SERVER: 192.168.1.1#53(192.168.1.1)

With nslookup:

nslookup example.com

Look for:

Server:  192.168.1.1
Address: 192.168.1.1#53

With host:

host -v example.com

Look for output similar to:

Using domain server:
Name: 192.168.1.1
Address: 192.168.1.1#53

Network Command Quick Book 🌐

BASICS

Common DNS record types

Quick examples

BASIC LOOKUP

Query the default A record for a domain

RECORD TYPES

Query an A record explicitly

Query an AAAA record for IPv6

Query mail exchange records

Query nameserver records

Query the start of authority record

Query TXT records

SHORT OUTPUT

Show only the answer section

Show only short MX answers

USING A SPECIFIC DNS SERVER

Ask Google Public DNS directly

Ask Cloudflare DNS directly

REVERSE LOOKUP

Resolve an IP address back to a host name

TRACE DNS RESOLUTION

Trace the full resolution path from the root servers

CHECK ALL SECTIONS

Display answer, authority, and additional sections clearly

COMMON FLAGS

Skip comments and show only records

Show DNSSEC-related records

PRACTICAL CHECKS

Verify a website points to the expected IP

Verify a domain has mail routing configured

Verify a TXT record such as SPF or domain verification

NSLOOKUP EXAMPLES

Use nslookup for a basic lookup

Query a specific record type

Query using a specific DNS server

HOST EXAMPLES

Use host for a basic lookup

Use host for MX records

Reverse lookup an IP address

See which DNS server answered you

Query the default `A` record for a domain

Query an `A` record explicitly

Query an `AAAA` record for IPv6

Use `nslookup` for a basic lookup

Use `host` for a basic lookup

Use `host` for MX records