312-50V10 · Question #136
You perform a scan of your company's network and discover that TCP port 123 is open. What services by default run on TCP port 123?
The correct answer is C. Network Time Protocol. Port 123 is assigned to the Network Time Protocol (NTP), which synchronizes clocks across networked systems.
Question
You perform a scan of your company's network and discover that TCP port 123 is open. What services by default run on TCP port 123?
Options
- ATelnet
- BPOP3
- CNetwork Time Protocol
- DDNS
How the community answered
(40 responses)- A8% (3)
- B3% (1)
- C85% (34)
- D5% (2)
Why each option
Port 123 is assigned to the Network Time Protocol (NTP), which synchronizes clocks across networked systems.
Telnet uses TCP port 23 for remote terminal access, not port 123.
POP3 (Post Office Protocol version 3) uses TCP port 110 for email retrieval, not port 123.
Network Time Protocol (NTP) is officially assigned to port 123 by IANA and uses it for time synchronization between clients and servers. While NTP primarily operates over UDP 123, the port assignment for TCP 123 also belongs to NTP. It is used by operating systems and network devices to maintain accurate system time across a network.
DNS uses TCP and UDP port 53 for domain name resolution, not port 123.
Concept tested: Well-known TCP/UDP port number assignments
Source: https://www.iana.org/assignments/service-names-port-numbers/service-names-port-numbers.xhtml
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