CCNA Network Services and Security Practice Question
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?
⚠ Common exam trap
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.
Answer choices
Why each option matters
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.
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
Adjacent-channel interference is the likely culprit because the 2.4 GHz band provides only three non-overlapping channels (1, 6, and 11); if an AP is configured on channel 3, it overlaps both channels 1 and 6, forcing clients to contend with simultaneous signals. This causes excessive frame collisions and retransmissions, which severely degrade throughput and latency even though clients maintain their association to the SSID. The mismatch between successful association and poor performance points directly to a Layer 1 RF problem rather than a higher-layer failure.
- ✗
A DHCP exhaustion problem on the WLAN
Why it's wrong here
DHCP exhaustion would surface as clients being unable to obtain an IP address after association, resulting in limited or no network connectivity for newly joined devices. The reported symptom—all users connecting but suffering throughput collapse—affects even devices that already hold valid leases, and DHCP does not influence the physical-layer RF channel utilization or signal quality. Therefore, while a DHCP shortage could prevent some clients from getting addresses, it cannot explain a uniform RF performance collapse across the wireless site.
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
An authentication mismatch between APs and clients would prevent clients from completing the 802.1X or WPA2/WPA3 handshake, so they would not progress beyond association to a full connection. The scenario explicitly states that users can connect to the SSID, meaning security credentials and authentication methods have been validated successfully. Because the failure occurs after successful authentication, the root cause cannot be an authentication mismatch; it must be something that degrades the RF medium, such as adjacent-channel interference.
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
A missing default route on the wireless controller would not affect local RF efficiency; it would only prevent traffic destined for networks beyond the controller's directly connected subnets from being forwarded. Since the reported issue is a decline in wireless performance for all users, which is a Layer 1 and Layer 2 phenomenon, the absence of a default gateway is irrelevant to the RF characteristics of the airspace. Clients would still associate, authenticate, and transmit at full data rates to the AP; only outbound routing would fail.
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
Adjacent-channel interference is the likely culprit because the 2.4 GHz band provides only three non-overlapping channels (1, 6, and 11); if an AP is configured on channel 3, it overlaps both channels 1 and 6, forcing clients to contend with simultaneous signals. This causes excessive frame collisions and retransmissions, which severely degrade throughput and latency even though clients maintain their association to the SSID. The mismatch between successful association and poor performance points directly to a Layer 1 RF problem rather than a higher-layer failure.
✗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?”
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JA
Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
This 200-301 practice question is part of Courseiva's free Cisco 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 200-301 exam.