What Is a Defining Characteristic of Wi-Fi Channels?

Correct Answer Analysis

Option B is correct because Wi-Fi networks utilize Carrier Sense Multiple Access with Collision Avoidance (CSMA/CA). Unlike switched Ethernet where each port is its own collision domain, all wireless clients associated with the same SSID and operating on the same frequency channel share the radio medium. Consequently, they compete for airtime and reside in a single contention domain, which networking exams classify as a collision domain.

Why Other Options Are Incorrect

Option A is false because the 2.4-GHz band typically offers only 11 to 13 channels regionally, with only three being truly non-overlapping (channels 1, 6, and 11 in North America). Option C is incorrect because channel spacing varies by band and regulation. In the 2.4-GHz band, channels are spaced 5 MHz apart, while the 5-GHz band uses 20 MHz increments for basic operation, expanding to 40, 80, or 160 MHz widths. Option D misrepresents the 5-GHz spectrum, which provides significantly more than 11 channels across multiple U-NII bands (often 20–31+ depending on local regulations), as noted by community contributors.

Community Validation

As highlighted in the exam discussion threads, candidates unanimously agree on Option B, recognizing it as a foundational concept tested across Cisco wireless certifications. The high agreement rate reflects the straightforward nature of this RF principle when compared to the clearly flawed numerical distractors.