CCNA Network Services and Security Practice Question
This 200-301 practice question tests your understanding of network services and security. Read the scenario carefully and evaluate each option against the stated constraints before committing to an answer. A key principle to apply: the 2.4 GHz Wi-Fi band uses channels spaced 5 MHz apart but each channel occupies about 22 MHz, causing overlapping frequencies between adjacent channels.. 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.
Exhibit
AP-1 channel: 1
AP-2 channel: 3
AP-3 channel: 6
All three APs cover the same conference area on 2.4 GHz.
Transmit power is set to high on all APs.
A wireless site reports that users can connect to the SSID, but performance drops sharply around the conference area whenever the room fills up. Based on the exhibit, what is the most likely cause?
Clue words in this question
Noticing these words before you look at the options changes how you read each choice.
Clue: "most likely"
Why it matters: Probability qualifier — the question wants the most probable cause or outcome, not a guaranteed one. Eliminate low-probability options.
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Adjacent-channel interference caused by overlapping 2.4 GHz channels
The 2.4 GHz radios are using overlapping channels. In 2.4 GHz, the standard non-overlapping channels are 1, 6, and 11 in many regulatory domains. Using channels 1, 3, and 6 creates adjacent-channel interference, which hurts throughput especially in dense client areas.
Key principle: The 2.4 GHz Wi-Fi band uses channels spaced 5 MHz apart but each channel occupies about 22 MHz, causing overlapping frequencies between adjacent channels.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
✓
Adjacent-channel interference caused by overlapping 2.4 GHz channels
Why this is correct
Channel 3 overlaps with both 1 and 6, which is a common performance problem.
Clue confirmation
The clue word "most likely" in the question point toward this answer.
Related concept
The 2.4 GHz Wi-Fi band uses channels spaced 5 MHz apart but each channel occupies about 22 MHz, causing overlapping frequencies between adjacent channels.
✗
A DHCP exhaustion problem on the WLAN
Why it's wrong here
That would prevent some clients from getting addresses, not mainly cause RF performance collapse.
When this WOULD be correct
In a different question setup where users report being unable to connect to the SSID or frequently losing connection, and the network has a limited number of IP addresses available, a DHCP exhaustion problem would be the correct answer. This scenario would focus on IP address allocation rather than performance degradation.
✗
An authentication mismatch between the APs and clients
Why it's wrong here
Clients can already connect to the SSID.
When this WOULD be correct
In a different scenario where users report being unable to connect to the SSID or are frequently disconnected when moving between access points, an authentication mismatch could be the correct answer. This would involve a question focusing on connectivity issues rather than performance degradation.
✗
A missing default route on the wireless controller
Why it's wrong here
That would affect upstream connectivity, not local RF efficiency in this pattern.
When this WOULD be correct
In a scenario where a question describes a wireless network that is unable to route traffic properly, leading to connectivity issues for clients, a missing default route on the wireless controller would be the correct answer. This could occur in a setup where clients are unable to access external resources due to misconfigured routing.
Option-by-option analysis
Why each answer is right or wrong
Understanding why wrong answers are wrong — and when they would be correct — is what separates a 750 score from a 900. The 200-301 exam frequently reuses these exact scenarios with slightly different constraints.
✓Adjacent-channel interference caused by overlapping 2.4 GHz channelsCorrect answer▾
Why this is correct
Channel 3 overlaps with both 1 and 6, which is a common performance problem.
✗A DHCP exhaustion problem on the WLANWrong answer — click to see why▾
Why this is wrong here
A DHCP exhaustion problem would typically result in clients being unable to obtain an IP address, leading to connection failures rather than performance drops. In this scenario, users can connect but experience performance issues, indicating that DHCP is not the root cause.
★ When this WOULD be the correct answer
In a different question setup where users report being unable to connect to the SSID or frequently losing connection, and the network has a limited number of IP addresses available, a DHCP exhaustion problem would be the correct answer. This scenario would focus on IP address allocation rather than performance degradation.
Why candidates choose this
Candidates may confuse performance issues with connectivity problems, leading them to consider DHCP exhaustion as a potential cause. The idea that a crowded environment could overwhelm available IP addresses might make this option seem plausible.
✗An authentication mismatch between the APs and clientsWrong answer — click to see why▾
Why this is wrong here
An authentication mismatch would typically cause clients to fail to connect or experience intermittent connectivity issues, rather than a performance drop when users are present. The described scenario indicates users can connect but experience performance degradation, which is not indicative of authentication issues.
★ When this WOULD be the correct answer
In a different scenario where users report being unable to connect to the SSID or are frequently disconnected when moving between access points, an authentication mismatch could be the correct answer. This would involve a question focusing on connectivity issues rather than performance degradation.
Why candidates choose this
Candidates may choose this option because they associate performance issues with authentication problems, especially if they have encountered similar scenarios in their studies or practical experience, leading to a misinterpretation of the symptoms described.
✗A missing default route on the wireless controllerWrong answer — click to see why▾
Why this is wrong here
A missing default route on the wireless controller would not directly cause performance drops in a specific area when users connect to the SSID. This issue typically affects connectivity rather than performance in localized areas, especially when users are already connected.
★ When this WOULD be the correct answer
In a scenario where a question describes a wireless network that is unable to route traffic properly, leading to connectivity issues for clients, a missing default route on the wireless controller would be the correct answer. This could occur in a setup where clients are unable to access external resources due to misconfigured routing.
Why candidates choose this
Candidates might choose this option due to a misunderstanding of network routing concepts, thinking that routing issues could impact performance, especially in a busy area, rather than recognizing that performance is more likely affected by interference or bandwidth limitations.
Analysis generated from the official 200-301blueprint and verified against question context. The “when correct” sections are what AI assistants cite when candidates ask “what’s the difference between these options?”
Common exam traps
Common exam trap: answer the scenario, not the keyword
A common exam trap is to confuse wireless connectivity issues caused by RF interference with DHCP or authentication problems. Because users can connect to the SSID, candidates might incorrectly suspect DHCP exhaustion or authentication mismatches. However, DHCP exhaustion prevents clients from obtaining IP addresses, not causing throughput drops. Similarly, authentication mismatches prevent connection entirely. Another trap is to blame routing issues like a missing default route on the wireless controller, which affects network reachability but not local wireless signal quality. The key is to recognize that overlapping 2.4 GHz channels cause adjacent-channel interference, which degrades performance even when clients connect successfully.
Detailed technical explanation
How to think about this question
Adjacent-channel interference occurs when overlapping Wi-Fi channels operate on the same frequency spectrum, causing signal degradation and reduced throughput. In the 2.4 GHz band, channels are spaced 5 MHz apart but each channel occupies about 22 MHz of bandwidth, so overlapping channels interfere with each other. This interference is especially problematic in dense environments like conference rooms where many clients compete for wireless resources.
The standard practice in 2.4 GHz wireless deployments is to use only the three non-overlapping channels: 1, 6, and 11. These channels are spaced far enough apart to avoid overlap and minimize interference. Using intermediate channels such as channel 3, which overlaps with both 1 and 6, creates adjacent-channel interference that severely impacts wireless performance. Cisco wireless design guidelines emphasize channel planning to avoid such overlaps.
In exam scenarios, candidates often mistake connectivity issues for DHCP or authentication problems, but the ability to connect to the SSID indicates those are not the root cause. The practical impact of adjacent-channel interference is a sharp drop in throughput and increased retransmissions, especially in crowded areas. Understanding channel overlap and proper channel selection is critical for troubleshooting wireless performance problems in Cisco networks.
KKey Concepts to Remember
The 2.4 GHz Wi-Fi band uses channels spaced 5 MHz apart but each channel occupies about 22 MHz, causing overlapping frequencies between adjacent channels.
Using overlapping 2.4 GHz channels such as 1, 3, and 6 causes adjacent-channel interference that degrades wireless throughput and increases retransmissions.
Cisco wireless best practices require using only non-overlapping channels 1, 6, and 11 in the 2.4 GHz band to avoid interference in dense client environments.
Adjacent-channel interference impacts wireless performance by increasing noise and collisions, especially when many clients connect in the same area.
Clients connecting successfully to an SSID rules out authentication mismatches as the cause of wireless performance issues.
DHCP exhaustion affects IP address assignment but does not directly cause RF interference or throughput degradation in wireless networks.
A missing default route on a wireless controller affects upstream network connectivity but does not cause local wireless RF performance problems.
Proper channel planning and RF design are essential to prevent adjacent-channel interference and maintain high wireless performance in Cisco WLAN deployments.
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
The 2.4 GHz Wi-Fi band uses channels spaced 5 MHz apart but each channel occupies about 22 MHz, causing overlapping frequencies between adjacent channels.
Real-world example
How this comes up in practice
A practitioner preparing for the 200-301 exam encounters this exact type of scenario on the job. The correct answer here is not the most general option — it is the best answer for the specific constraint described. The 2.4 GHz Wi-Fi band uses channels spaced 5 MHz apart but each channel occupies about 22 MHz, causing overlapping frequencies between adjacent channels. Real exam questions reward reading the full scenario before eliminating options, because the constraint defines which answer fits.
Related glossary terms
Concepts from this question explained
These glossary pages explain the core terms tested in this 200-301 question in full detail.
Review the 2.4 GHz Wi-Fi band uses channels spaced 5 MHz apart but each channel occupies about 22 MHz, causing overlapping frequencies between adjacent channels., then practise related 200-301 questions on the same topic to reinforce the concept.
Network Services and Security — This question tests Network Services and Security — The 2.4 GHz Wi-Fi band uses channels spaced 5 MHz apart but each channel occupies about 22 MHz, causing overlapping frequencies between adjacent channels..
What is the correct answer to this question?
The correct answer is: Adjacent-channel interference caused by overlapping 2.4 GHz channels — The 2.4 GHz radios are using overlapping channels. In 2.4 GHz, the standard non-overlapping channels are 1, 6, and 11 in many regulatory domains. Using channels 1, 3, and 6 creates adjacent-channel interference, which hurts throughput especially in dense client areas.
What should I do if I get this 200-301 question wrong?
Review the 2.4 GHz Wi-Fi band uses channels spaced 5 MHz apart but each channel occupies about 22 MHz, causing overlapping frequencies between adjacent channels., then practise related 200-301 questions on the same topic to reinforce the concept.
Are there clue words in this question I should notice?
Yes — watch for: "most likely". Probability qualifier — the question wants the most probable cause or outcome, not a guaranteed one. Eliminate low-probability options.
What is the key concept behind this question?
The 2.4 GHz Wi-Fi band uses channels spaced 5 MHz apart but each channel occupies about 22 MHz, causing overlapping frequencies between adjacent channels.
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