Free CWNP Certified Wireless Network Administrator CWNA-109 Exam Questions

A pre-design site visit in preparation for a predictive wireless LAN design is essential for gathering physical and environmental data about the site. The key tasks to be performed during such a visit include:

Evaluating Building Materials: Different materials (concrete, glass, wood, etc.) have varying effects on RF signal propagation. Understanding the materials present helps in accurately predicting how signals will behave within the environment.

Floor Plan Verification: Ensuring that the floor plan documents are an accurate representation of the actual building layout is crucial. Discrepancies between the floor plans and the physical layout can lead to inaccuracies in the predictive design.

The other options, while potentially valuable in other contexts, are not directly related to preparing for a predictive design:

Installing APs (option A) for testing co-channel interference is more aligned with an active site survey rather than a pre-design visit for a predictive design.

Collecting information about security requirements (option B) is important but is not directly related to the physical aspects of the site that would impact a predictive design.

Testing antenna types (option C) would typically be part of an active site survey or the actual deployment phase, not a pre-design visit for predictive modeling.

Therefore, option D is the correct answer, focusing on evaluating physical aspects crucial for accurate predictive modeling.

CWNA Certified Wireless Network Administrator Official Study Guide: Exam CWNA-109, by David D. Coleman and David

A . Westcott.

Best practices for conducting pre-design site visits in wireless network planning.

OFDMA is a new modulation scheme introduced in 802.11ax that allows multiple users to share the same channel by dividing it into smaller subchannels called resource units (RUs). This improves the efficiency and capacity of the WLAN by reducing contention and overhead. However, to use OFDMA, both the AP and the client must support 802.11ax and negotiate the parameters of the subchannel allocation.Therefore, the customer needs to upgrade the clients that require OFDMA to 802.11ax devices12.

The other options are not correct because they do not reflect the reality of OFDMA.Option B is incorrect because OFDMA is a mandatory feature of 802.11ax for both downlink and uplink transmissions, and all 802.11ax APs must support it1. Option C is incorrect because OFDM and OFDMA are different modulation schemes, and OFDM does not allow multiple users to share the same channel.Option D is incorrect because 802.11ac devices cannot support OFDMA through driver upgrades, as they lack the hardware and firmware capabilities to do so2.

VHT TXOP (Very High Throughput Transmit Opportunity) power save is a feature introduced with the 802.11ac amendment, which is designed to improve the power efficiency of devices connected to a WLAN. This feature enhances battery life in several ways, compared to the legacy Power Save mode:

Enhanced Power Saving: VHT TXOP power save allows devices to disable more components of the WLAN transceiver when they are in a low power state. This reduces the power consumption during periods when the device is not actively transmitting or receiving data.

Intelligent Wake-Up Mechanisms: It employs more sophisticated mechanisms for devices to determine when they need to wake up and listen to the channel, further reducing unnecessary power usage.

Optimized Operation: This power save mode is optimized for the high-throughput environment of 802.11ac networks, allowing devices to efficiently manage power while maintaining high performance.

Legacy Power Save mode, introduced in earlier versions of the 802.11 standards, does not provide the same level of component disablement or the intelligent wake-up mechanisms found in VHT TXOP power save, making option B the correct answer.

IEEE 802.11ac-2013 Amendment: Enhancements for Very High Throughput for Operation in Bands below 6 GHz.

CWNA Certified Wireless Network Administrator Official Study Guide: Exam CWNA-109, by David D. Coleman and David A. Westcott.

What is always required to establish a high quality 2.4 GHz RF link at a distance of 3 miles (5 kilometers) isa Fresnel Zone that is at least 60% clear of obstructions. The Fresnel Zone is an elliptical-shaped area around the line-of-sight path between two antennas that reflects and refracts the RF waves. The Fresnel Zone radius depends on the frequency of the RF signal and the distance between the antennas. For optimal performance, the Fresnel Zone should be at least 60% clear of any obstructions that may cause interference, attenuation, or multipath fading. The minimum output power level, antenna gain, and antenna type may vary depending on the environmental conditions and regulatory constraints, but they are not always required for a high quality RF link.Reference:[CWNP Certified Wireless Network Administrator Official Study Guide: Exam CWNA-109], page 75; [CWNA: Certified Wireless Network Administrator Official Study Guide: Exam CWNA-109], page 65.

The device in the bridge implementation that acts as the 802.1X Authenticator is theroot bridge. The root bridge is the bridge that connects to the wired network and acts as the central point for all other bridges in the point-to-multipoint topology. The root bridge authenticates the non-root bridges using 802.1X/EAP and forwards their authentication requests to the RADIUS server. The non-root bridges act as the 802.1X Supplicants and use EAP methods such as EAP-TLS or EAP-PEAP to authenticate with the root bridge.Reference:[CWNP Certified Wireless Network Administrator Official Study Guide: Exam CWNA-109], page 459; [Cisco Aironet Wireless Bridges FAQ], question 29.

A possible cause of a sudden change in performance for the laptop computers is thata new tenant in the building has set their AP to the same RF channel that your customer is using. This can create co-channel interference (CCI), which is a situation where two or more APs or devices use the same or overlapping channels in the same area. CCI can degrade the performance of WLANs by increasing contention, collisions, retransmissions, and latency. CCI can also reduce the effective range and throughput of WLANs by lowering the signal-to-noise ratio (SNR). To avoid or mitigate CCI, it is recommended to use non-overlapping channels, adjust transmit power levels, or implement channel management techniques such as dynamic frequency selection (DFS) or load balancing. The sky condition, antenna position, or Bluetooth headset are not likely to cause a sudden change in performance for the laptop computers.Reference:[CWNP Certified Wireless Network Administrator Official Study Guide: Exam CWNA-109], page 81; [CWNA: Certified Wireless Network Administrator Official Study Guide: Exam CWNA-109], page 71.

Refraction is the bending of an RF signal as it passes through a medium with a different density than free space. This can cause the signal to change its direction and speed, which can affect the accuracy and reliability of wireless communication.Refraction is influenced by factors such as temperature, humidity, and atmospheric pressure12.Reference:CWNA-109 Study Guide, Chapter 2: Radio Frequency Fundamentals, page 72;CWNA-109 Study Guide, Chapter 2: Radio Frequency Fundamentals, page 67.

DHCP (Dynamic Host Configuration Protocol) is a commonly used method to locate the controllers by the APs in a WLAN that is implemented using wireless controllers. DHCP is a protocol that allows a device to obtain an IP address and other network configuration parameters from a server. In a wireless controller scenario, the APs can use DHCP to request an IP address from a DHCP server, which can also provide the IP address or hostname of the wireless controller as an option in the DHCP response. This way, the APs can discover the wireless controller and establish a connection with it.Alternatively, the APs can also use other methods to locate the wireless controller, such as DNS (Domain Name System), broadcast or multicast discovery, or manual configuration.Reference:1, Chapter 8, page 309;2, Section 5.2

In addition to coverage analysis results, what should be included in a post-deployment site survey report to ensure WLAN users experience acceptable performance isCapacity analysis results. Capacity analysis is a method of testing the ability of the WLAN to support the expected number and type of users, devices, and applications. Capacity analysis can help to determine the optimal number and placement of access points, the appropriate channel and power settings, the required QoS policies, and the expected throughput and latency levels. Capacity analysis results can help to verify that the WLAN meets the performance requirements and service level agreements (SLAs) of the organization.Reference:[CWNP Certified Wireless Network Administrator Official Study Guide: Exam CWNA-109], page 548; [CWNA: Certified Wireless Network Administrator Official Study Guide: Exam CWNA-109], page 518.

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.

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.