Nokia Certified Network Associate (NCNA) — Question 37

Which of the following is the best description of well known ports?

Answer options

• A. Well known ports apply to routers only and are used for communication and control traffic. Well known port numbers are assigned by IANA and can have any value.
• B. Well known ports are used by TCP and UDP. Well known port numbers range from 1024 to 65535 and are assigned by IANA.
• C. Well known port numbers are used by both TCP and UDP. Well known port numbers range from 1 to 1023 and are assigned by IANA.
• D. Well known ports numbers are used by TCP only. Well known port numbers are assigned by IANA and can have any value.

Correct answer: C

Explanation

The correct answer is C because well known port numbers range from 1 to 1023 and are indeed used by both TCP and UDP. Options A and D incorrectly limit the scope to routers and TCP only, while option B misstates the range of well known ports as starting from 1024.