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Which server port does DNS use with both UDP and TCP?

DNS uses port 53 with UDP and TCP.

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  1. Port 25
  2. Port 67
  3. Port 53 ✔

Why: Standard DNS queries commonly use UDP port 53 because it has low overhead. DNS also uses TCP port 53 when reliable stream transport is required.

Huh, didn't know that: The transport protocol is part of an endpoint, so UDP 53 and TCP 53 are distinct sockets.

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DNS found port 53 by looking up its number.
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References

Answer: Port 53. Standard DNS queries commonly use UDP port 53 because it has low overhead. DNS also uses TCP port 53 when reliable stream transport is required.

  1. RFC 1035: Domain Names, Implementation and Specification www.rfc-editor.org/rfc/rfc1035.html
    The Internet supports name server access using TCP [RFC-793] on server port 53 (decimal) as well as datagram access using UDP [RFC-768] on UDP port 53 (decimal).
    Checked 2026-10-11.

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