The correct answer is 802.11n, also known as Wi-Fi 4, because it was the first IEEE standard to natively support both the 2.4 GHz and 5 GHz frequency bands simultaneously, making it the dual band backward compatible solution you are looking for. It achieves this through MIMO (Multiple Input Multiple Output) technology, which uses multiple antennas to improve throughput and range, while its mandatory support for legacy modulation schemes like DSSS/CCK on 2.4 GHz and OFDM on 5 GHz ensures it works seamlessly with older 802.11a/b/g devices. On the CompTIA Network+ N10-009 exam, this question tests your understanding of Wi-Fi evolution and frequency band support—a common trap is confusing 802.11ac (which only operates on 5 GHz) or 802.11ax (Wi-Fi 6, which is dual band but not the first). A simple memory tip: think "n for both bands" or remember that 802.11n is the "n-ovice" standard that introduced dual-band operation.
N10-009 Network Implementation Practice Question
This N10-009 practice question tests your understanding of network implementation. Read the scenario carefully and evaluate each option against the stated constraints before committing to an answer. After answering, compare your reasoning against the explanation and wrong-answer breakdown below. Once you have made your selection, read the full explanation to reinforce the concept and understand why each distractor is designed to mislead on exam day.
A company is deploying a wireless network that must support both 2.4 GHz and 5 GHz frequency bands. Which IEEE 802.11 standard supports both bands and is backward compatible with older devices?
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
C) 802.11n
802.11n (Wi-Fi 4) is the correct answer because it was the first standard to natively support both 2.4 GHz and 5 GHz bands simultaneously, using MIMO (Multiple Input Multiple Output) technology. It also maintains backward compatibility with older 802.11a/b/g devices through mandatory support for legacy modulation schemes (DSSS/CCK for 2.4 GHz and OFDM for 5 GHz).
Key principle: Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
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A) 802.11b
Why it's wrong here
802.11b operates only in the 2.4 GHz band and has a maximum throughput of 11 Mbps.
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B) 802.11g
Why it's wrong here
802.11g operates only in the 2.4 GHz band, though it is backward compatible with 802.11b.
✓
C) 802.11n
Why this is correct
802.11n supports both 2.4 GHz and 5 GHz and offers higher throughput than earlier standards.
Related concept
Read the scenario before looking for a memorised answer.
✗
D) 802.11ac
Why it's wrong here
802.11ac operates exclusively in the 5 GHz band and is not backward compatible with 2.4 GHz devices.
Common exam traps
Common exam trap: answer the scenario, not the keyword
The trap here is that candidates often confuse 802.11g (which is backward compatible with 802.11b but only 2.4 GHz) with a dual-band standard, or incorrectly assume 802.11ac supports 2.4 GHz because it is often marketed as 'dual-band' in consumer devices, but the IEEE 802.11ac-2013 amendment defines operation only in the 5 GHz band.
Detailed technical explanation
How to think about this question
802.11n introduced HT (High Throughput) modes with channel bonding (40 MHz channels), short guard intervals, and up to 4 spatial streams, achieving theoretical data rates up to 600 Mbps. A subtle behavior is that when 802.11n operates in mixed mode (with legacy devices present), it must use protection mechanisms like RTS/CTS or CTS-to-self to avoid collisions, which reduces throughput. In real-world deployments, dual-band 802.11n access points are common for bridging legacy 2.4 GHz clients while offering higher performance on 5 GHz.
KKey Concepts to Remember
Read the scenario before looking for a memorised answer.
Find the constraint that changes the correct option.
Eliminate answers that are true in general but not in this case.
TExam Day Tips
→Watch for words such as best, first, most likely and least administrative effort.
→Review why wrong options are wrong, not only why the correct option is correct.
Key takeaway
Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Real-world example
How this comes up in practice
A small business has 20 workstations on the 192.168.1.0/24 network and one public IP from its ISP. The router uses PAT (NAT overload) so all 20 devices share one public address using different source ports. NAT questions test whether you understand the four address terms and which direction each translation applies.
Related glossary terms
Concepts from this question explained
These glossary pages explain the core terms tested in this N10-009 question in full detail.
Network Implementation — This question tests Network Implementation — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: C) 802.11n — 802.11n (Wi-Fi 4) is the correct answer because it was the first standard to natively support both 2.4 GHz and 5 GHz bands simultaneously, using MIMO (Multiple Input Multiple Output) technology. It also maintains backward compatibility with older 802.11a/b/g devices through mandatory support for legacy modulation schemes (DSSS/CCK for 2.4 GHz and OFDM for 5 GHz).
What should I do if I get this N10-009 question wrong?
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
What is the key concept behind this question?
Read the scenario before looking for a memorised answer.
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This N10-009 practice question is part of Courseiva's free CompTIA certification practice question bank. Courseiva provides original exam-style practice questions with explanations, topic-based practice, mock exams, readiness tracking, and study analytics to help learners prepare for the N10-009 exam.
Question Discussion
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