DNS primarily uses UDP port 53 for most query/response operations. However, TCP port 53 is also used, particularly for larger responses (such as DNS zone transfers or DNSSEC).
A.✔UDP – Used for standard DNS queries due to lower overhead.
B.✔TCP port 53 – Used when UDP is insufficient, especially for zone transfers (AXFR/IXFR).
Extract from MTCNA Course Material – DNS and Networking Services:
“DNS typically uses UDP/53, but falls back to TCP/53 for larger queries or zone transfers.”
Extract from MikroTik Wiki – DNS Settings:
“DNS uses UDP for general queries. TCP is used when UDP cannot accommodate the size of the response.”
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