SK0-004 · Question #412
An administrator is securing a network time server by disabling ports. After completing this process, the network time server is not functioning. The administrator should now go back and verify…
The correct answer is C. 123. NTP (Network Time Protocol) operates exclusively on UDP port 123, so disabling that port will break time synchronization services.
Question
An administrator is securing a network time server by disabling ports. After completing this process, the network time server is not functioning. The administrator should now go back and verify whether which of the following ports is enabled?
Options
- A23
- B110
- C123
- D389
How the community answered
(20 responses)- B5% (1)
- C90% (18)
- D5% (1)
Why each option
NTP (Network Time Protocol) operates exclusively on UDP port 123, so disabling that port will break time synchronization services.
Port 23 is used by Telnet, a remote terminal protocol unrelated to time synchronization.
Port 110 is used by POP3 for email retrieval and has no role in network time services.
Port 123 is the well-known port assigned to NTP by IANA. Both NTP clients and servers send and receive time synchronization packets on this UDP port. Without port 123 enabled, the time server cannot communicate with clients or upstream time sources.
Port 389 is used by LDAP for directory services and is not involved in time protocol communications.
Concept tested: NTP port number and time server configuration
Source: https://www.iana.org/assignments/service-names-port-numbers/service-names-port-numbers.xhtml
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