CWNA-109 Exam Dumps : Certified Wireless Network Administrator

S1G is one of the 802.11 PHYs that is more likely to be used in an industrial deployment but not likely to be used in standard office deployments. This is because S1G stands for Sub-1 GHz, which means it operates in the frequency bands below 1 GHz, such as 900 MHz and 868 MHz. These bands offer better penetration and range than the higher frequency bands used by other 802.11 PHYs, such as 2.4 GHz and 5 GHz. This makes S1G suitable for industrial applications that require robust and reliable wireless communication in harsh environments, such as factories, warehouses, mines, and smart grids. S1G also supports low-power and low-data-rate devices, such as sensors, actuators, and meters, which are common in industrial Internet of Things (IoT) scenarios. VHT, OFDM, and HT are other 802.11 PHYs that are more commonly used in standard office deployments, as they offer higher data rates and capacity than S1G, but have lower range and penetration. References: CWNA-109 Study Guide, Chapter 3: Radio Frequency Technologies, page 751

In the 2.4 GHz frequency band used for 802.11 wireless networks, the channel bandwidth is typically 20 MHz, but the actual frequency spread of each channel is about 22 MHz due to the modulation techniques used. This spread causes overlap between adjacent channels, which can lead to interference and degrade network performance. To avoid this, it's essential to use non-overlapping channels.

The three non-overlapping channels in the 2.4 GHz band are 1, 6, and 11. Each of these channels is spaced sufficiently apart to avoid interference with each other:

Channel 1: Centered at 2.412 GHz.

Channel 6: Centered at 2.437 GHz.

Channel 11: Centered at 2.462 GHz.

Given the options provided, option C (1 and 5) is the closest to a pair of non-overlapping channels, although in practice, channel 5 would still cause some interference with channel 1 due to the 22 MHz spread. The ideal choice for non-overlapping channels would be any two channels among 1, 6, and 11, but this is not an option provided. Therefore, within the given options, 1 and 5 are the best choice, understanding that in a real-world scenario, 1 and 6 or 6 and 11 would be preferred to avoid overlap.

The authentication method that is referenced in the 802.11-2016 and 802.11-2020 specifications and is recommended for robust WLAN client security is 802.1X/EAP. 802.1X/EAP stands for IEEE 802.1X Port-Based Network Access Control with Extensible Authentication Protocol and is a framework that provides strong authentication and dynamic encryption key generation for WLAN clients. 802.1X/EAP involves three parties: the supplicant (the client), the authenticator (the AP or the controller), and the authentication server (usually a RADIUS server). The supplicant sends its credentials (such as username and password, certificate, or token) to the authenticator, which forwards them to the authentication server. The authentication server verifies the credentials and sends a response to the authenticator, which grants or denies access to the supplicant. The authentication server also generates a master key that is used to derive encryption keys for the data frames between the supplicant and the authenticator. 802.1X/EAP supports various EAP methods that offer different levels of security and flexibility, such as EAP-TLS, EAP-PEAP, EAP-TTLS, EAP-FAST, and EAP-SIM. SSL, IPSec, and WEP are not authentication methods, but rather encryption or security protocols that are not specific to WLANs or referenced in the 802.11 specifications. References: [CWNP Certified Wireless Network Administrator Official Study Guide: Exam CWNA-109], page 299; [CWNA: Certified Wireless Network Administrator Official Study Guide: Exam CWNA-109], page 289.