Domain Name System (DNS) requests can use protocol/port:

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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