The Domain Name System (DNS) translates human-readable domain names into IP addresses that computers use to communicate, serving as the internet's directory service. Operating through a globally distributed hierarchy of servers—from root servers through TLDs to authoritative nameservers—DNS enables virtually every internet interaction. Understanding DNS record types, zone management, resolution flows, security mechanisms like DNSSEC, and troubleshooting techniques is essential for network administrators, security professionals, and developers building resilient internet infrastructure. DNS performance, caching behavior, and attack surface remain critical concerns as the protocol continues evolving with privacy enhancements and security extensions.
What This Cheat Sheet Covers
This topic spans 17 focused tables and 103 indexed concepts. Below is a complete table-by-table outline of this topic, spanning foundational concepts through advanced details.
Table 1: Core DNS Record Types
| Type | Example | Description |
|---|---|---|
example.com. 300 IN A 93.184.216.34 | • Maps a hostname to an IPv4 address • most fundamental DNS record used for web hosting and service endpoints. | |
example.com. 300 IN AAAA 2606:2800:220:1:248:1893:25c8:1946 | • Maps a hostname to an IPv6 address (128-bit) • essential as IPv4 addresses become exhausted. | |
www.example.com. 300 IN CNAME example.com. | • Creates an alias pointing to another domain name • cannot coexist with other records at the same name • not allowed at zone apex in standard DNS. | |
example.com. 3600 IN MX 10 mail.example.com. | • Specifies mail servers for the domain with priority values (lower = higher priority) • multiple MX records provide failover. | |
example.com. 300 IN TXT "v=spf1 include:_spf.google.com ~all" | • Holds arbitrary text data • commonly used for SPF, DKIM, DMARC, domain verification, and security policies. |