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What should be inspected to verify proper configuration is DNS. DNS stands for Domain Name System and is a service that resolves hostnames to IP addresses. In a controller-based AP deployment, DNS can be used to help the AP locate the controller by using a predefined hostname such as CISCO-CAPWAP-CONTROLLER or aruba-master. The AP sends a DNS query for this hostname and receives an IP address of the controller as a response. Therefore, if DNS is not configured properly or if there is no DNS entry for the controller hostname, the AP may not be able to locate the controller. NTP, BOOTP, and AP hosts file are not relevant for this scenario. References: [CWNP Certified Wireless Network Administrator Official Study Guide: ExamCWNA-109], page 374; [CWNA: Certified Wireless Network Administrator Official Study Guide: ExamCWNA-109], page 364.

Patch and panel antennas are directional antenna types that are commonly used by indoor Wi-Fi devices in a MIMO multiple spatial stream implementation. These antennas have a flat rectangular shape and can be mounted on walls or ceilings to provide coverage in a specific direction. They have a moderate gain and a relatively wide beamwidth, making them suitable for multipath environments where signals can reflect off different surfaces and create multiple spatial streams. Patch and panel antennas can also support polarization diversity, which means they can transmit and receive both horizontally and vertically polarized waves, increasing the MIMO performance. References: 1, Chapter 2, page 72; 2, Section 2.4

SAE (Simultaneous Authentication of Equals) is required when operating 802.11ax APs in the 6 GHz band using passphrase-based authentication. SAE is a secure and robust authentication method that is defined in the IEEE 802.11s amendment and is also known as WPA3-Personal or WPA3-SAE. SAE is based on a cryptographic technique called Dragonfly Key Exchange, which allows two parties to establish a shared secret key using a passphrase, without revealing the passphrase or the key to an eavesdropper or an attacker. SAE also provides forward secrecy, which means that if the passphrase or the key is compromised in the future, it does not affect the security of past communications.

SAE is required when operating 802.11ax APs in the 6 GHz band using passphrase-based authentication because of the new regulations and standards that apply to this band. The 6 GHz band is a new frequency band that was opened for unlicensed use by the FCC and other regulatory bodies in 2020. The 6 GHz band offers more spectrum and less interference than the existing 2.4 GHz and 5 GHz bands, which can enable higher performance and efficiency for Wi-Fi devices. However, the 6 GHz band also has some restrictions and requirements that are different from the other bands, such as:

The 6 GHz band is divided into two sub-bands: U-NII-5 (5925-6425 MHz) and U-NII-7 (6525-6875 MHz). The U-NII-5 sub-band is subject to DFS (Dynamic Frequency Selection) rules, which require Wi-Fi devices to monitor and avoid using channels that are occupied by radar systems or other primary users. The U-NII-7 sub-band is not subject to DFS rules, but it has a lower maximum transmit power limit than the U-NII-5 sub-band.

The Wi-Fi devices that operate in the 6 GHz band are called 6E devices, which stands for Extended Spectrum. 6E devices must support 802.11ax technology, which is also known as Wi-Fi 6 or High Efficiency (HE). 802.11ax is a new standard that improves the performance and efficiency of Wi-Fi networks by using features such as OFDMA (Orthogonal Frequency Division Multiple Access), MU-MIMO (Multi-User Multiple Input Multiple Output), BSS Coloring, TWT (Target Wake Time), and HE PHY and MAC enhancements.

The 6E devices that operate in the 6 GHz band must also support WPA3 security, which is a new security protocol that replaces WPA2 and provides stronger encryption and authentication for Wi-Fi networks. WPA3 has two modes: WPA3-Personal and WPA3-Enterprise. WPA3-Personal uses SAE as its authentication method, which requires a passphrase to establish a secure connection between two devices. WPA3-Enterprise uses EAP (Extensible Authentication Protocol) as its authentication method, which requires a certificate or a credential to authenticate with a server.

Therefore, SAE is required when operating 802.11ax APs in the 6 GHz band using passphrase-based authentication because it is part of WPA3-Personal security, which is mandatory for 6E devices in this band. References: , Chapter 3, page 120; , Section 3.2

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FT (Fast Transition) is an IEEE 802.11 standard method for fast roaming. FT is defined in the IEEE 802.11r amendment and is also known as Fast BSS Transition (FBT) or Fast Secure Roaming. FT is a feature that allows a client station to quickly switch from one AP to another within the same ESS (Extended Service Set) without having to re-authenticate and re-associate with each AP. This reduces the latency and packet loss that may occur during roaming, thus improving the user experience and maintaining the security of the connection. FT works by using pre-authentication and key caching mechanisms that allow the client station and the APs to exchange security information before the actual roaming occurs. This way, when the client station decides to roam to a new AP, it can use a fast reassociation request and response that contain only a few fields, instead of a full authentication and association exchange that require more time and data. References: 1, Chapter 9, page 367; 2, Section 6.3

 The most effective method for testing roaming in relation to 802.11 VoIP handsets is to place a call with the handset and move around the facility to test quality duringroaming. This method allows you to evaluate the actual performance and user experience of VoIP calls over wireless networks, as well as identify any potential issues such as signal strength, interference, latency, jitter, packet loss, or handoff delays. A spectrum analyzer can only show you the RF activity during a VoIP call, but not how it affects the voice quality or roaming behavior. A protocol analyzer can capture the traffic generated when a laptop roams, but it cannot simulate the characteristics of a VoIP handset such as battery life, antenna design, codec support, or QoS features. A built-in roaming monitor is not a common feature in all VoIP handsets, and it may not provide accurate or comprehensive information about the roaming process. References: [CWNP Certified Wireless Network Administrator Official Study Guide: ExamCWNA-109], page 487; [Voice over Wireless LAN 4.1 Design Guide], page 6-19.

The IEEE 802.11ax standard, also known as High-Efficiency Wireless (HEW) or simply HE, includes support for operation across multiple frequency bands: 2.4 GHz, 5 GHz, and, with the appropriate regulatory approvals, the 6 GHz band. This makes option D the correct answer. Here's how it compares to the other options:

HE (802.11ax): Introduced as an enhancement over previous standards, 802.11ax is designed to improve efficiency, especially in dense environments. It supports operation in the 2.4 GHz, 5 GHz, and 6 GHz bands (the latter pending regulatory approval in various regions), making it highly versatile and future-proof.

VHT (802.11ac): Very High Throughput, or 802.11ac, operates exclusively in the 5 GHz band. It introduced significant speed improvements over its predecessor (802.11n) but does not support the 2.4 GHz or 6 GHz bands.

HT (802.11n): High Throughput, or 802.11n, supports operation in both the 2.4 GHz and 5 GHz bands. However, it does not include support for the 6 GHz band.

HR/DSSS (802.11b): High-Rate Direct Sequence Spread Spectrum, or 802.11b, operates only in the 2.4 GHz band. It was one of the early Wi-Fi standards and does not support 5 GHz or 6 GHz bands.

Given these distinctions, only 802.11ax (option D) supports operation across all three mentioned bands, aligning with the requirements stated in the question.

References:

IEEE 802.11ax-2021: High-Efficiency Wireless LAN Medium Access Control (MAC) and Physical Layer (PHY) Specifications.

Understanding the 802.11ax (Wi-Fi 6) standard and its implications for modern wireless networking.

Return loss is a measure of how well the components of an RF system are matched in terms of their impedance. Impedance is the opposition to the flow of alternating current in a circuit, and it depends on the frequency, resistance, capacitance, and inductance of the components. When the impedance of the source, the transmission line, and the load are not equal, some of the power is reflected back to the source, causing a loss of forward power. This loss is expressed in decibels (dB) as return loss. The higher the return loss, the lower the reflection and the better the impedance matching. Conversely, the lower the return loss, the higher the reflection and the worse the impedance matching.

VSWR (Voltage Standing Wave Ratio) is another way of expressing the same concept. It is the ratio of the maximum voltage to the minimum voltage along a transmission line due to the interference of the incident and reflected waves. A VSWR of 1:1 means that there is no reflection and perfect impedance matching. A VSWR higher than 1:1 means that there is some reflection and impedance mismatch. The higher the VSWR, the higher the reflection and the lower the return loss.

Therefore, a significant impedance mismatch between components in an RF system will cause high reflection, high VSWR, and low return loss.

The WLAN feature that would allow the network administrator to control the network resources that can be accessed by each employee based on their department is Role-Based Access Control (RBAC). RBAC is a method of assigning different permissions and policies to users or groups based on their roles in the organization. RBAC can be implemented by using VLANs, ACLs, or firewalls to restrict access to certain network segments or resources. RBAC can also be integrated with 802.1X/EAP authentication to dynamically assign roles and VLANs to users based on their credentials. References: [CWNP Certified Wireless Network Administrator Official Study Guide: ExamCWNA-109], page 403; [Role-Based Access Control (RBAC) in Wireless Networks], page 1.

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: ExamCWNA-109], page 299; [CWNA: Certified Wireless Network Administrator Official Study Guide: ExamCWNA-109], page 289.

An immediate concern that you note after hearing this information is that the power budget in the edge switches must be carefully planned and monitored based on the number of supported PoE devices. PoE stands for Power over Ethernet and is a technology that allows Ethernet switches to deliver power along with data to devices such as VoIP phones and 802.11 access points. PoE devices are classified into different classes based on their power consumption and output. The edge switches have a limited power budget that determines how many PoE devices they can support simultaneously. If the power budget is exceeded, some PoE devices may not receive enough power or may shut down unexpectedly. Therefore,it is important to plan and monitor the power budget in the edge switches based on the number and class of PoE devices connected to them. Using Ether-channel, placing switches in optimal locations, or avoiding distortion are not immediate concerns related to PoE devices. References: [CWNP Certified Wireless Network Administrator Official Study Guide: ExamCWNA-109], page 234; [CWNA: Certified Wireless Network Administrator Official Study Guide: ExamCWNA-109], page 224.