CompTIA Security Plus Mock Test Q142

A security technician needs to open ports on a firewall to allow for domain name resolution. Which of the following ports should be opened? (Select TWO).

A. TCP 21
B. TCP 23
C. TCP 53
D. UDP 23
E. UDP 53

Correct Answer: C,E
Section: Network Security

Explanation:
DNS uses TCP and UDP port 53. TCP port 53 is used for zone transfers, whereas UDP port 53 is used for queries.

Incorrect Answers:
A: FTP uses TCP port 21.
B. D: Telnet uses port 23.

References:
Stewart, James Michael, CompTIA Security+ Review Guide, Sybex, Indianapolis, 2014, p. 51
http://en.wikipedia.org/wiki/List_of_TCP_and_UDP_port_numbers