dig & nslookup

~12 min · dig, nslookup, dns, record-types

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DNS query tools

Track 1 introduced DNS conceptually. dig is how you actually query it. The most common usage is dig +short hostname — just give me the IP. The advanced flags let you query specific record types, bypass your default resolver, or trace the full delegation chain.

Record types worth knowing

Type	Returns
A	IPv4 address(es)
AAAA	IPv6 address(es)
MX	Mail servers
NS	Authoritative nameservers
TXT	Text records (SPF, DKIM, domain verification)
CNAME	Canonical name aliases
PTR	Reverse DNS

Code

dig and nslookup recipes·bash

# Standard query
dig github.com

# Short answer only
dig +short github.com

# Specific record type
dig github.com MX
dig github.com NS
dig github.com TXT
dig github.com AAAA

# Use a specific resolver (Cloudflare)
dig @1.1.1.1 +short github.com
dig @8.8.8.8 +short github.com

# Reverse — IP to name
dig -x 140.82.121.3

# Trace the full delegation chain (root → TLD → authoritative)
dig +trace github.com

# Simpler tool, more limited
nslookup github.com
nslookup github.com 1.1.1.1

External links

dig manual

Exercise

Run dig +short github.com, dig github.com MX, dig github.com NS, dig +trace github.com. Read the trace output and identify: root server → .com TLD → GitHub's authoritative nameservers → final answer. The whole DNS delegation chain in one command — internalize that picture and DNS issues stop being magic.