Question

Difficulty: EasyTroubleshooting Wireless Connectivity and Signal Issues

A network technician deploys three wireless access points across an office building to provide coverage on the 2.4 GHz band. Users report frequent packet loss, slow speeds, and dropped connections when moving near areas covered by multiple access points. Upon inspecting the wireless controller, the technician observes that the access points are manually configured to operate on channels 1, 2, and 3, respectively. Which of the following is the most likely cause of the wireless performance degradation?

  1. A
    DHCP scope exhaustion preventing wireless clients from acquiring valid IP addresses when roaming between access points.
  2. B
    An incorrect STP root bridge priority configuration causing Layer 2 switching loops across access point trunk ports.
  3. Adjacent-channel interference caused by using overlapping channels in the 2.4 GHz frequency spectrum.Answer
  4. D
    An implicit deny rule on the wireless network security gateway blocking inter-access point roaming frames.

Answer

Adjacent-channel interference caused by using overlapping channels in the 2.4 GHz frequency spectrum.
In the 2.4 GHz frequency band, standard 20 MHz channels require a 25 MHz separation between channel centers to avoid overlapping. Consequently, only channels 1, 6, and 11 are non-overlapping. Setting adjacent access points to channels 1, 2, and 3 causes severe adjacent-channel interference (ACI), resulting in corrupted Wi-Fi frames, excessive retransmissions, and performance degradation in areas where signals overlap.

Step-by-Step Solution

1
Analyze the wireless spectrum configuration provided in the scenario.
The access points are set to channels 1, 2, and 3 in the 2.4 GHz band.
The 2.4 GHz Wi-Fi spectrum consists of 11 channels in North America (13 globally), each 20 MHz wide but spaced only 5 MHz apart.
2
Identify non-overlapping channels for 2.4 GHz wireless deployments.
Channels 1, 6, and 11 are the standard non-overlapping 20 MHz channels.
Channels 1, 2, and 3 share overlapping frequency ranges, causing adjacent-channel interference (ACI) where signals bleed into neighbouring frequencies.
3
Correlate channel overlap with the observed symptoms.
Adjacent-channel interference leads to frame corruption, retransmissions, high latency, and dropped connections in overlapping coverage zones.
Using channels 1, 6, and 11 eliminates adjacent-channel interference between nearby access points.

Key Concept

2.4 GHz Wireless Channel Overlap and Interference
Estimated Time:45s
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