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🗓️ 04102025 0030

DNS TOOLS

Tools for querying DNS (Domain Name System) to resolve hostnames to IP addresses.

dig - DNS Lookup (Most Powerful)​

Commands​

dig example.com              # A record (IPv4)
dig example.com MX           # Mail servers
dig example.com NS           # Nameservers
dig @8.8.8.8 example.com    # Query Google DNS
dig +trace example.com       # Full resolution path
dig +short example.com       # Concise output
dig example.com ANY          # All available records

Use for: DNS troubleshooting, checking propagation, verifying records.

Interpreting Output​

$ dig example.com

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

;; ANSWER SECTION:
example.com.            86400   IN      A       93.184.216.34

;; Query time: 12 msec
;; SERVER: 8.8.8.8#53(8.8.8.8)
;; WHEN: Fri Oct 04 00:30:00 SGT 2025
;; MSG SIZE  rcvd: 56

Key parts:

  • QUESTION SECTION: What you asked for (A record for example.com)
  • ANSWER SECTION: The response
    • example.com. - The domain (trailing dot = fully qualified)
    • 86400 - TTL (Time To Live) in seconds (how long to cache)
    • IN - Internet class
    • A - Record type (IPv4 address)
    • 93.184.216.34 - The actual IP address
  • Query time: How long the query took
  • SERVER: Which DNS server responded

Common record types:

  • A - IPv4 address
  • AAAA - IPv6 address
  • MX - Mail server (with priority number)
  • NS - Nameserver
  • CNAME - Canonical name (alias)
  • TXT - Text records (SPF, DKIM, verification)

Troubleshooting tips:

  • No ANSWER section? → Domain doesn't exist or no record of that type
  • NXDOMAIN status? → Domain doesn't exist (see networking_etc_hosts for workaround)
  • SERVFAIL status? → DNS server error
  • High query time? → DNS server slow or network issues (use networking_connectivity tools)

nslookup - Simple DNS Lookup​

Commands​

nslookup example.com         # Simple lookup
nslookup example.com 8.8.8.8 # Query specific DNS server
nslookup -type=MX example.com   # Mail records
nslookup -type=NS example.com   # Nameservers

Use for: Quick DNS checks when you don't need dig's detail. Cross-platform (Windows/Mac/Linux).

Interpreting Output​

$ nslookup example.com
Server:         8.8.8.8
Address:        8.8.8.8#53

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

Key parts:

  • Server: DNS server that answered your query
  • Non-authoritative answer: Response from cache (not the authoritative nameserver)
  • Name: The domain you queried
  • Address: The resolved IP address

host - Simple DNS Lookup​

Commands​

host example.com             # Simple lookup
host -t MX example.com       # Mail records
host -t NS example.com       # Nameservers
host -a example.com          # All records

Use for: Even simpler than nslookup, clean one-line output.

Interpreting Output​

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

$ host -t MX example.com
example.com mail is handled by 10 mail.example.com.

Key parts:

  • Direct, human-readable output
  • For MX records: Number (e.g., 10) is priority (lower = higher priority)

whois - Domain Registration Info​

Commands​

whois example.com            # Domain registration info
whois 8.8.8.8               # IP ownership

Use for: Finding domain owner, expiration date, registrar information.

Interpreting Output​

$ whois example.com

Domain Name: EXAMPLE.COM
Registry Domain ID: 2336799_DOMAIN_COM-VRSN
Registrar: RESERVED-Internet Assigned Numbers Authority
Creation Date: 1995-08-14T04:00:00Z
Registry Expiry Date: 2023-08-13T04:00:00Z
Registrar: IANA
Registrar Abuse Contact Email: abuse@iana.org

Name Server: A.IANA-SERVERS.NET
Name Server: B.IANA-SERVERS.NET

Registrant Organization: Internet Assigned Numbers Authority
Registrant State/Province: CA
Registrant Country: US

Key information:

  • Creation Date: When domain was first registered
  • Registry Expiry Date: When domain expires (if not renewed)
  • Name Server: Authoritative DNS servers for this domain
  • Registrant: Who owns the domain
  • Registrar: Company managing the registration

Use cases:

  • Check if domain is about to expire
  • Find who to contact about a domain
  • Verify nameservers are correct
  • Check IP block ownership

References​