CompTIA Network+ Practice Test

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What port number does DNS typically use for standard queries?

UDP/53
TCP/53
UDP/67
UDP/123

The correct answer is: UDP/53

DNS, which stands for Domain Name System, primarily uses port 53 for its operations. For standard queries, DNS typically operates over the User Datagram Protocol (UDP) on port 53. This is because DNS queries are generally small, and UDP is a connectionless protocol that allows for quicker transmission and lower latency, which is ideal for the rapid querying of domain names. While DNS can also use TCP on port 53, particularly for larger data transfers such as zone transfers or when responses exceed 512 bytes, standard queries are usually made over UDP. This distinction is essential for understanding DNS functionality, as it optimizes the speed and efficiency of name resolution without the overhead associated with establishing a TCP connection. The other port numbers listed are associated with different protocols and functionalities. For instance, UDP port 67 is used for the DHCP server, and UDP port 123 is used for the Network Time Protocol (NTP), neither of which serves the DNS query purpose.