CompTIACompTIA
N10-009 · Question #517
N10-009 Question #517: Real Exam Question with Answer & Explanation
The correct answer is C: 255.255.248.0. A /21 mask uses 21 network bits; in dotted decimal that is 255.255.248.0 (the third octet has five 1s: 11111000 = 248).
Submitted by stefanr· Mar 6, 2026Networking Concepts
Question
An administrator needs to configure an IoT device with a /21 subnet mask, but the device will only accept dotted decimal notation. Which of the following subnet masks should the administrator use?
Options
- A255.255.224.0
- B255.255.240.0
- C255.255.248.0
- D255.255.252.0
Explanation
A /21 mask uses 21 network bits; in dotted decimal that is 255.255.248.0 (the third octet has five 1s: 11111000 = 248).
Community Discussion
No community discussion yet for this question.