ISC2 CC Network Security Practice Question
Which common port is used by DNS and which transport layer protocol does it primarily use?
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
✓
Port 53, both UDP and TCP
DNS uses port 53 and primarily uses UDP for queries, though TCP is used for zone transfers.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
Port 53, UDP only
Why it's wrong here
DNS also uses TCP for zone transfers, but primarily UDP.
- ✗
Port 161, UDP
Why it's wrong here
Port 161 is SNMP.
- ✓
Port 53, both UDP and TCP
Why this is correct
Correct. DNS uses UDP for queries and TCP for zone transfers.
- ✗
Port 53, TCP only
Why it's wrong here
DNS uses UDP primarily.
Go deeper
Related to this question
Learn chapter
Security Governance and Compliance
Key term
TCP
TCP is a connection-oriented transport layer protocol that ensures reliable, ordered, and error-checked delivery of data between applications over IP networks.
Key term
DNS
DNS is the system that translates human-friendly domain names like example.com into machine-readable IP addresses so computers can find each other on a network.
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Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
This CC 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 CC exam.