An IT technician is troubleshooting persistent performance degradation and high packet ret… — CompTIA Network+

An IT technician is troubleshooting persistent performance degradation and high packet retransmission rates affecting legacy handheld inventory scanners in a logistics warehouse. The scanners operate exclusively on the $2.4\text{ GHz}$ band. A wireless spectrum analysis reveals severe co-channel and adjacent-channel interference across the facility, with channel utilization exceeding $85\%$ . Inspection of the wireless controller configuration shows that the $2.4\text{ GHz}$ radios on three neighboring Access Points (APs) are configured to use $40\text{ MHz}$ channel bonding set to primary Channel 3. Which of the following is the primary root cause of the wireless connectivity issues?

Configuring $40\text{ MHz}$ channel bonding on the $2.4\text{ GHz}$ band consumes 8 out of the 11 available channels, causing unavoidable adjacent-channel interference with almost all standard channel assignments.Answer
B
The access points are triggering Dynamic Frequency Selection (DFS) radar events on Channel 3, forcing the $2.4\text{ GHz}$ radios to drop connected client sessions.
C
The handheld inventory scanners are experiencing authentication dropouts because WPA3-Enterprise RADIUS authentication is incompatible with the $2.4\text{ GHz}$ frequency spectrum.
D
The access points are failing to assign APIPA addresses to the inventory scanners due to a mismatch between the primary channel bandwidth and the DHCP scope range.

Answer

Configuring

40\text{ MHz}

channel bonding on the

2.4\text{ GHz}

band consumes 8 standard channels, creating unavoidable adjacent-channel interference across the limited

2.4\text{ GHz}

spectrum.

In the

2.4\text{ GHz}

Wi-Fi band, channels are spaced

5\text{ MHz}

apart, and a standard

20\text{ MHz}

channel requires

20\text{ MHz}

of separation to avoid overlapping adjacent channels (yielding non-overlapping channels 1, 6, and 11). Configuring a

40\text{ MHz}

channel width spans 8 adjacent channels simultaneously, overlapping with almost all available channels in the

2.4\text{ GHz}

spectrum and causing high frame corruption and retransmission rates due to adjacent-channel interference.

Step-by-Step Solution

Analyze the physical radio frequency parameters reported in the scenario.

The deployment uses

40\text{ MHz}

channel widths on the

2.4\text{ GHz}

band centered around Channel 3.

Understanding the channel layout of the

2.4\text{ GHz}

band is necessary to evaluate RF interference.

Calculate the spectral footprint of a

40\text{ MHz}

channel in the

2.4\text{ GHz}

band.

The

2.4\text{ GHz}

spectrum (Channels 1–11 in North America) has only

60\text{ MHz}

of total usable bandwidth for non-overlapping channels (

20\text{ MHz}

per channel for Channels 1, 6, and 11). A single

40\text{ MHz}

channel occupies 8 overlapping

5\text{ MHz}

channels (e.g., Channels 1 through 8).

Enabling

40\text{ MHz}

channels on

2.4\text{ GHz}

prevents the deployment of non-overlapping channels and causes severe adjacent-channel interference (ACI) with any nearby

20\text{ MHz}

40\text{ MHz}

APs.

Identify the recommended best practice for

2.4\text{ GHz}

channel width configuration.

Wi-Fi best practices dictate restricting

2.4\text{ GHz}

radios strictly to

20\text{ MHz}

channel widths using non-overlapping channels 1, 6, and 11.

Restricting channel width to

20\text{ MHz}

eliminates adjacent-channel overlap and allows CSMA/CA to properly manage co-channel medium sharing.

Key Concept

2.4 GHz Channel Width and Adjacent-Channel Interference (ACI)

Question

Answer

Step-by-Step Solution

Key Concept

Common Mistakes

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