DNS TCP queries use which port and protocol?

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Prepare for the CPSA Port Numbers Exam with quizzes on port numbers, services, and protocols. Each question is accompanied by hints and detailed explanations. Get exam-ready with our comprehensive study tool!

Multiple Choice

DNS TCP queries use which port and protocol?

Explanation:
DNS uses port 53 and can run over either UDP or TCP. For standard, quick queries the protocol is UDP on port 53. When reliability is needed or a UDP response would be too large (causing truncation), DNS uses TCP on port 53. So for DNS queries specifically conducted over TCP, the correct pairing is port 53 with the TCP protocol. The other options mix different services or transport protocols (HTTP on 80, SSH on 22, or DNS over UDP on 53 UDP), which don’t describe DNS over TCP.

DNS uses port 53 and can run over either UDP or TCP. For standard, quick queries the protocol is UDP on port 53. When reliability is needed or a UDP response would be too large (causing truncation), DNS uses TCP on port 53. So for DNS queries specifically conducted over TCP, the correct pairing is port 53 with the TCP protocol. The other options mix different services or transport protocols (HTTP on 80, SSH on 22, or DNS over UDP on 53 UDP), which don’t describe DNS over TCP.

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