SSCP Network and Communications Security Practice Question
Which UDP port is used by the Domain Name System (DNS) for name resolution queries?
⚠ Common exam trap
Candidates often confuse DNS with other common UDP services — candidates who memorize port numbers loosely may pick UDP 67 (DHCP) or UDP 123 (NTP) under time pressure.
Answer choices
Why each option matters
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
UDP 53
DNS uses UDP port 53 for standard name resolution queries because the request and response are small and UDP's low overhead is ideal for the query-response pattern. TCP port 53 is used only for zone transfers (AXFR/IXFR), DNSSEC responses exceeding 512 bytes, or when the TC (truncated) bit forces a TCP retry.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
UDP 161
Why it's wrong here
UDP 161 carries SNMP, used for polling network devices, not DNS name resolution. It tempts because SNMP is a common UDP service an administrator meets daily, and port numbers in the 160s are easily confused with DNS's well-known 53 under exam pressure.
- ✗
UDP 67
Why it's wrong here
UDP 67 is the DHCP server port, used to allocate IP addresses and options to clients, not to resolve names. It tempts because DHCP and DNS are both core UDP services configured together, so the port is familiar even though it serves address assignment.
- ✓
UDP 53
Why this is correct
DNS name resolution queries use UDP port 53 for standard lookups, with TCP 53 reserved for zone transfers and responses exceeding 512 bytes. This satisfies the stem's requirement for the specific UDP port used in resolution queries.
- ✗
UDP 123
Why it's wrong here
UDP 123 carries NTP, used for clock synchronisation between hosts and time servers, not DNS queries. It tempts because NTP is ubiquitous infrastructure traffic, and its low, well-known port number sits close to DNS's 53, making it an easy misremembering.
Visual reference
Go deeper
Related to this question
About these practice questions
This SSCP question is part of Courseiva's 971-question bank — original exam-style content with full explanations and wrong-answer analysis, never real exam questions or exam dumps. Learn why practice questions differ from exam dumps →
JA
Written and reviewed by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
Last reviewed September 2026 · checked against the official ISC2 exam blueprint
This SSCP practice question is part of Courseiva's free ISC2 certification practice question bank. Courseiva provides original exam-style practice questions with explanations, topic-based practice, mock exams, readiness tracking, and study analytics to help learners prepare for the SSCP exam.