Question 46 of 1,389
CCNA Network Infrastructure and Connectivity Practice Question
Exhibit
WLC# show ap radio summary AP Name Slot Radio Channel Power Clients Channel Util Noise Interference AP-1 0 802.11b 1 17 12 15% -95 10% AP-1 1 802.11a 36 15 8 85% -87 70% AP-2 0 802.11b 6 17 10 12% -94 8% AP-2 1 802.11a 36 15 9 82% -88 68% AP-3 0 802.11b 11 17 14 14% -96 9% AP-3 1 802.11a 40 15 7 30% -90 15% AP-4 0 802.11b 1 17 11 13% -95 10% AP-4 1 802.11a 36 15 8 80% -87 72%
A network administrator is troubleshooting a wireless connectivity issue in a large office. Users on the 5 GHz band report intermittent disconnections and slow performance, while 2.4 GHz clients are unaffected. The office uses a Cisco 9800 WLC with APs that support 802.11ac Wave 2. The administrator checks the WLC's RF profile and notices a high number of channel utilization reports on channel 36. What is the most likely cause of the problem?
⚠ Common exam trap
Cisco often tests the misconception that DFS channels are the solution for any 5 GHz interference issue, but the trap here is that high channel utilization on a non-DFS channel (36) indicates co-channel interference, not radar avoidance.
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
✓
Change some APs to use channels 40, 44, or 48 to reduce co-channel interference.
Channel 36 is a 20 MHz channel in the 5 GHz band. When many APs use the same channel (channel 36), they share the same medium, leading to co-channel interference (CCI). This causes intermittent disconnections and slow performance for 5 GHz clients because they must contend for airtime. Spreading APs across non-overlapping channels like 40, 44, or 48 reduces CCI and improves performance.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
Enable DFS channels to avoid radar interference.
Why it's wrong here
DFS (Dynamic Frequency Selection) channels are specifically intended for radar interference avoidance, not for mitigating co-channel interference between APs. The exhibit shows no radar events; enabling DFS would introduce unnecessary radar-detect downtime and channel unavailability without changing the fact that multiple APs share the same non-DFS channel. The root cause is poor channel planning, not radar coexistence.
- ✓
Change some APs to use channels 40, 44, or 48 to reduce co-channel interference.
Why this is correct
Co-channel interference (CCI) occurs when multiple APs with overlapping coverage use the same 5 GHz channel, causing them to contend for the same half-duplex medium. By changing some APs to channels 40, 44, or 48, you spread the cells across the four non-overlapping UNII-1/UNII-3 channels, reducing contention and enabling more efficient airtime use. This directly mitigates the excessive retries and throughput degradation shown in the exhibit.
- ✗
Increase the channel width to 160 MHz to improve throughput.
Why it's wrong here
Increasing the channel width to 160 MHz would enlarge the RF footprint and consume most of the available 5 GHz spectrum, but it would not address the existing co-channel contention between APs. In fact, wider channels reduce the number of non-overlapping channels available (often to just one 160 MHz block per regulatory domain), which would increase CCI and make the problem worse. The exhibit's issue is channel reuse, not insufficient channel bandwidth.
- ✗
Disable the 2.4 GHz radios to force all clients to 5 GHz.
Why it's wrong here
Disabling the 2.4 GHz radios only removes the legacy band and does nothing to alter the channel assignments on the 5 GHz band where the contention is occurring. This would also force clients that depend on 2.4 GHz (such as IoT or older devices) onto 5 GHz, potentially causing connectivity issues while leaving the 5 GHz co-channel interference completely unsolved. The exhibit's problem is AP-to-AP channel overlap on 5 GHz, not the presence of the 2.4 GHz band.
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.
✓Change some APs to use channels 40, 44, or 48 to reduce co-channel interference.Correct answer▾
Why this is correct
Co-channel interference (CCI) occurs when multiple APs with overlapping coverage use the same 5 GHz channel, causing them to contend for the same half-duplex medium. By changing some APs to channels 40, 44, or 48, you spread the cells across the four non-overlapping UNII-1/UNII-3 channels, reducing contention and enabling more efficient airtime use. This directly mitigates the excessive retries and throughput degradation shown in the exhibit.
✗Enable DFS channels to avoid radar interference.Wrong answer — click to see why▾
Why this is wrong here
DFS channels are used to avoid radar interference, but the problem described is co-channel interference on channel 36, not radar events. The exhibit shows no radar events, so enabling DFS channels would not address the high channel utilization.
Why candidates choose this
Students may confuse DFS with dynamic channel assignment or think that DFS helps with interference in general, but DFS specifically handles radar detection and avoidance, not co-channel interference.
✗Increase the channel width to 160 MHz to improve throughput.Wrong answer — click to see why▾
Why this is wrong here
Increasing channel width to 160 MHz would actually increase the likelihood of co-channel interference because fewer non-overlapping channels are available, and it would not solve the existing high utilization on channel 36.
Why candidates choose this
Students might think wider channels always improve throughput, but in dense environments, wider channels exacerbate interference and are not recommended without proper planning.
✗Disable the 2.4 GHz radios to force all clients to 5 GHz.Wrong answer — click to see why▾
Why this is wrong here
Disabling 2.4 GHz radios would force all clients to 5 GHz, potentially worsening the co-channel interference on channel 36 by adding more clients to an already congested channel. The 2.4 GHz band is not the source of the problem.
Why candidates choose this
Some might think that moving all clients to 5 GHz would improve performance, but without addressing the channel reuse issue, it would only increase congestion on the 5 GHz band.
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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Last reviewed: Jun 11, 2026
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