Dig¶

dig (Domain Information Groper) is a powerful command-line tool used for querying DNS (Domain Name System) servers. It is commonly used by network administrators, cybersecurity professionals, and developers to perform DNS lookups, troubleshoot DNS-related issues, and verify DNS configurations.

It replaces older tools like nslookup and host due to its flexibility, advanced query options, and structured output.

Key Features¶

Performs DNS lookups for A, AAAA, MX, TXT, NS, CNAME, SOA, and other record types
Queries specific DNS servers
Displays detailed query and response sections
Supports reverse DNS lookups
Enables trace mode for following the resolution path step-by-step
Allows batch queries using input files

Basic Syntax¶

dig [@server] [domain] [type]

Where:

@server – (optional) DNS server to query (e.g., @8.8.8.8 for Google DNS)
domain – Domain name to query (e.g., example.com)
type – Record type to query (e.g., A, MX, NS, etc.)

Common Usage Examples¶

1. Basic A Record Lookup¶

Retrieve the IP address of a domain:

dig example.com

Explanation:
This queries the default DNS server for the A record of example.com.

2. Query a Specific DNS Server¶

Use a specific DNS server like Google DNS (8.8.8.8):

dig @8.8.8.8 example.com

Explanation:
This sends the DNS query to Google’s public DNS server instead of the system’s default resolver.

3. Lookup Specific Record Types¶

MX Record (Mail Exchange):

dig example.com MX

NS Record (Name Server):

dig example.com NS

TXT Record:

dig example.com TXT

Explanation:
Specifying the record type retrieves only that specific type of DNS record.

4. Reverse DNS Lookup¶

Find the domain name associated with an IP address:

dig -x 8.8.8.8

Explanation:
Performs a reverse DNS lookup on the given IP address.

5. Short Answer (Simplified Output)¶

Get only the essential answer:

dig +short example.com

Explanation:
The +short option suppresses all detailed sections and displays only the IP or record value.

6. Trace the DNS Resolution Path¶

View each step of DNS resolution:

dig +trace example.com

Explanation:
Displays how the query travels from the root servers to the authoritative server.

7. Show Only the Answer Section¶

dig example.com +noall +answer

Explanation:
Suppresses all output except the final answer, useful for scripting or clean results.

8. Check Multiple Domains from a File¶

dig -f domains.txt

Explanation:
Performs DNS lookups for all domains listed in domains.txt (one domain per line).

9. Query Specific Port (Non-Standard DNS)¶

dig @8.8.8.8 -p 5353 example.com

Explanation:
Specifies a non-default port (useful for testing DNS servers on different ports).

Output Breakdown¶

Typical dig output contains several sections:

Header: Status of query (NOERROR, SERVFAIL, etc.)
QUESTION SECTION: Shows what was asked
ANSWER SECTION: Displays the resolved records
AUTHORITY SECTION: Lists authoritative name servers
ADDITIONAL SECTION: Includes extra information like IPs of name servers

Practical Use Cases¶

Penetration Testing: Identify DNS misconfigurations or information leaks
Network Diagnostics: Verify DNS resolution or detect propagation delays
System Administration: Check MX or NS records for email or domain configuration
Incident Response: Trace domain redirections or phishing domain origins

Example Output¶

$ dig example.com +noall +answer

example.com.     3600    IN    A    93.184.216.34

Summary¶

Task	Command Example	Description
Basic lookup	`dig example.com`	Get A record
Specific server	`dig @8.8.8.8 example.com`	Query Google DNS
Mail records	`dig example.com MX`	Get mail servers
Reverse lookup	`dig -x 8.8.8.8`	Get domain from IP
Trace query	`dig +trace example.com`	Follow DNS resolution
Short output	`dig +short example.com`	Clean output

nslookup – Older DNS query tool
host – Simplified DNS lookup command
whois – Retrieves domain registration details