dig

Overview

The dig (Domain Information Groper) command is a flexible tool for interrogating DNS name servers. It performs DNS lookups and displays the answers from the name servers.

Syntax

dig [@server] [name] [type] [options]

Common Options

Option Description
+short Short answer
+noall Set all display flags off
+answer Display answer section
+norecurse Turn off recursive processing
+trace Trace delegation path
+noquestion Don’t show question section
+nocmd Don’t show command line
+nocomments Don’t show comment lines
-t type Set query type
-x addr Reverse lookup
-p port Port number
-4 IPv4 query
-6 IPv6 query

Key Use Cases

  1. DNS troubleshooting
  2. Record verification
  3. DNS propagation
  4. DNSSEC validation
  5. Zone transfers

Examples with Explanations

Example 1: Basic Query

dig google.com

Look up A records

Example 2: Specific Record

dig domain.com MX

Look up mail servers

Example 3: Trace Path

dig +trace domain.com

Show resolution path

Understanding Output

Sections in output: 1. Header (status, flags) 2. Question section 3. Answer section 4. Authority section 5. Additional section

Common Usage Patterns

  1. Short output:

    dig +short domain.com

  2. Reverse lookup:

    dig -x IP_address

  3. Specific server:

    dig @8.8.8.8 domain.com

Performance Analysis

  • Query time
  • Server response
  • Resolution path
  • DNSSEC validation
  • Answer completeness

Additional Resources

Best Practices

  1. Use specific queries
  2. Verify multiple servers
  3. Check DNSSEC
  4. Document results
  5. Compare responses

Troubleshooting

  1. Resolution failures
  2. DNSSEC issues
  3. Propagation delays
  4. Server problems
  5. Zone transfers

Query Types

  1. A (IPv4 address)
  2. AAAA (IPv6 address)
  3. MX (Mail exchange)
  4. NS (Name server)
  5. SOA (Start of authority)