What does DNS stand for?
DNS stands for Domain Name System. The system that translates names such as example.com into IP addresses. Attacks include cache poisoning and tunnelling; DNSSEC adds signed records.
DNS translates names into the data needed to reach a service, most often a name into an IP address. It is a distributed hierarchy: root servers, top-level domain servers and the authoritative servers for each domain, with resolvers that do the lookups for clients and cache the answers. It uses port 53, UDP for most queries and TCP for large responses and zone transfers. Common record types are A, AAAA, CNAME, MX and TXT.
DNS in practice: an example
A user types a site name. The laptop asks its resolver, which asks a root server, then the .com servers, then the domain's authoritative server, and returns the A record. The answer is cached for the time-to-live set by the domain owner, so the next lookup is immediate.
What DNS is confused with
DNS vs DHCP: what is the difference?
DHCP gives a device its IP address and settings, including which DNS server to use. DNS then resolves names. A device with an address but no name resolution has a DNS problem, not a DHCP one. What DHCP stands for
Which exams cover DNS?
DNS is on the official CompTIA acronym list for all four exams covered here.
- Security+ SY0-801: 2.5 (Threats, Vulnerabilities, and Attacks).
- CySA+ CS0-004: on the acronym list, not tied to one objective.
- Network+ N10-009: 1.0 (Networking Concepts); 3.0 (Network Operations); 4.0 (Network Security).
- A+ 220-1201 and 220-1202: 220-1201 2.0 (Networking); 220-1202 1.0 (Operating Systems); 220-1202 2.0 (Security).
Each number is a CompTIA exam objective and the name in brackets is its domain. The exam puts the term in a scenario; it does not ask you to recite the expansion.
Check yourself: two practice questions
Written by CertSprint for this page. They are not taken from any exam.
1. A user can open a website by typing its IP address but not its name. Which service should be checked first?
- DHCP
- DNS
- NTP
- SNMP
Show the answer
B. DNS. Connectivity works, so addressing and routing are fine. Only the name-to-address step is failing.
2. Which DNS record type directs email for a domain to its mail servers?
- A
- CNAME
- MX
- PTR
Show the answer
C. MX. MX records list the mail exchangers for a domain and their priority.
Sources: RFC 1034: Domain Names: Concepts and Facilities; NIST SP 800-81-2, Secure Domain Name System (DNS) Deployment Guide. The acronym and its expansion come from CompTIA's official acronym lists, linked from each exam glossary above. The explanation, example and questions are CertSprint's own, checked against these sources on 11 November 2026.