SY0-501 · Question #80
A technician must configure a firewall to block external DNS traffic from entering a network. Which of the following ports should they block on the firewall?
The correct answer is A. 53. To block external DNS traffic, a technician must configure the firewall to block port 53, which is the standard port for the Domain Name System.
Question
A technician must configure a firewall to block external DNS traffic from entering a network. Which of the following ports should they block on the firewall?
Options
- A53
- B110
- C143
- D443
How the community answered
(49 responses)- A82% (40)
- B6% (3)
- C10% (5)
- D2% (1)
Why each option
To block external DNS traffic, a technician must configure the firewall to block port 53, which is the standard port for the Domain Name System.
Port 53 is the well-known and default port used by the Domain Name System (DNS) for both UDP (for queries) and TCP (for zone transfers). Blocking this port on a firewall prevents external DNS requests from entering the network, effectively blocking DNS traffic.
Port 110 is used by the Post Office Protocol version 3 (POP3) for retrieving emails, not for DNS traffic.
Port 143 is used by the Internet Message Access Protocol (IMAP) for email retrieval, not for DNS traffic.
Port 443 is used by HTTPS (HTTP Secure) for secure web traffic, not for DNS traffic.
Concept tested: Identifying standard DNS port for firewall rules
Source: https://learn.microsoft.com/en-us/windows-server/identity/ad-ds/active-directory-ports-firewalls
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