A customer has an existing wireless network with a Cisco 9800 WLC high availability cluster...

Non-802.11 device detection on the 5 GHz band without a dedicated spectrum analyzer is possible through Cisco ' s CleanAir technology, which is embedded as an RF ASIC in many Cisco AP models including the 9120 series. CleanAir operates at the hardware layer — below the 802.11 MAC — enabling the APs to detect, classify, and report non-802.11 interference sources such as cordless phones, microwave ovens, video cameras, radar, and other unlicensed RF emitters in the 5 GHz spectrum. The WLC aggregates CleanAir reports from all APs and provides a consolidated interference device list accessible through the WLC ' s monitoring interface. Since the question specifies the 5 GHz band, the relevant 802.11 protocol for 5 GHz is 802.11a (and its successors 802.11n and 802.11ac). Exporting the list of 802.11a interferers from the WLC using the CleanAir RF ASIC correctly targets the 5 GHz band and identifies non-802.11 devices detected there. Option A incorrectly references 802.11b, which operates only on 2.4 GHz. Options B and C attempt to use the WLAN adapter for non-802.11 detection, but a standard WLAN adapter in monitor mode can only capture 802.11 frames — it cannot detect non-802.11 RF energy without a spectrum analyzer chipset. Reference: WLSD Study Guide — Cisco CleanAir Technology, Non-802.11 Interference Detection, Post-Deployment Survey Methodology.