Free Practice Questions for CWNP CWNA-109 Exam

The likely problem that causes this scenario is faulty drivers. Drivers are software components that enable the communication between the operating system and the hardware devices, such as the wireless adapters. Faulty drivers can cause various issues with the wireless connectivity, such as not detecting or connecting to certain networks, dropping connections, or reducing performance. Faulty drivers can be caused by corrupted files, outdated versions, incompatible settings, or hardware defects. To fix faulty drivers, you can try to update, reinstall, or roll back the drivers, or contact the manufacturer for support. Interference from non-Wi-Fi sources, DoS attack, or interference from other WLANs are not likely to cause this scenario, as they would affect all devices in the same area, not just the new laptops. References: [CWNP Certified Wireless Network Administrator Official Study Guide: ExamCWNA-109], page 562; [CWNA: Certified Wireless Network Administrator Official Study Guide: ExamCWNA-109], page 532.

VHT stands for Very High Throughput, which is a physical layer (PHY) specification that supports the 5 GHz frequency band and supports 80 MHz channels. VHT is used by the IEEE 802.11ac standard, which is also known as Wi-Fi 5. VHT allows for higher data rates and more spatial streams than the previous HT (High Throughput) PHY, which is used by the IEEE 802.11n standard, also known as Wi-Fi 4. HT supports the 2.4 GHz and 5 GHz bands, but only supports up to 40 MHz channels12

The other options are not correct because:

ERP (option C) stands for Extended Rate PHY, which is a physical layer specification that supports the 2.4 GHz frequency band and supports up to 20 MHz channels. ERP is used by the IEEE 802.11g standard, which is also known as Wi-Fi 3. ERP allows for higher data rates than the previous DSSS (Direct Sequence Spread Spectrum) PHY, which is used by the IEEE 802.11b standard, also known as Wi-Fi 234

OFDM (option D) stands for Orthogonal Frequency Division Multiplexing, which is a modulation technique that divides a signal into multiple subcarriers that are spaced orthogonally to each other. OFDM is not a physical layer specification, but a common feature of many PHY specifications, including ERP, HT, and VHT. OFDM allows for higher spectral efficiency and robustness against multipath interference than the previous CCK (Complementary Code Keying) modulation technique used by DSSS34

An advantage of using WPA3-Personal instead of WPA2-Personal as a security solution for 802.11 networks is that WPA3-Personal, also called WPA3-SAE, uses a stronger authentication exchange to better secure the network. WPA3-Personal uses Simultaneous Authentication of Equals (SAE) as the key exchange protocol, which provides stronger protection against offline dictionary attacks and password guessing than WPA2-Personal. SAE uses a Diffie-Hellman key exchange with elliptic curve cryptography (ECC) to establish a pairwise master key (PMK) between the AP and the client without revealing it to any eavesdropper. SAE also provides forward secrecy, which means that if one PMK is compromised, it does not affect the security of other PMKs. WPA2-Personal uses Pre-Shared Key (PSK) as the key exchangeprotocol, which is vulnerable to offline brute-force attacks if the passphrase is weak or leaked. Both WPA3-Personal and WPA2-Personal use AES for encryption, so there is no difference in that aspect. WPA3-Personal does not use a different encryption algorithm than WPA2-Personal, but rather a different key exchange protocol. References: [CWNP Certified Wireless Network Administrator Official Study Guide: ExamCWNA-109], page 307; [CWNA: Certified Wireless Network Administrator Official Study Guide: ExamCWNA-109], page 297.

The beamwidth of an RF antenna is the angular measure of how wide the main lobe of radiation is. The main lobe is the area where the signal strength is highest and most concentrated. The beamwidth is calculated at the points where the main lobe decreases power by 3 dB, which means it is half of the maximum power. The beamwidth can be measured in both horizontal and vertical planes, depending on how the antenna is oriented. The horizontal beamwidth is also called azimuth, while the vertical beamwidth is also called elevation. The beamwidth patterns on an antenna polar chart indicate how the RF energy is distributed in different directions. References: 1, Chapter 2, page 66; 2, Section 2.3

OFDM (Orthogonal Frequency Division Multiplexing) is the physical layer specification (PHY) that VHT capable devices must be backward compatible with according to the IEEE 802.11-2012 standard. VHT (Very High Throughput) is aPHY and MAC enhancement that is defined in the IEEE 802.11ac amendment and is also known as Wi-Fi 5. VHT operates only in the 5 GHz band and uses features such as wider channel bandwidths (up to 160 MHz), higher modulation schemes (up to 256-QAM), more spatial streams (up to eight), multi-user MIMO (MU-MIMO), beamforming, and VHT PHY and MAC enhancements. VHT can achieve data rates up to 6.9 Gbps.

According to the IEEE 802.11-2012 standard, VHT capable devices must be backward compatible with devices using OFDM PHY, which is defined in the IEEE 802.11a amendment and is also used by IEEE 802.11g, IEEE 802.11n, and IEEE 802.11h amendments. OFDM operates in both the 2.4 GHz and 5 GHz bands and uses features such as subcarriers, symbols, guard intervals, and OFDM PHY and MAC enhancements. OFDM can achieve data rates up to 54 Mbps.

Backward compatibility means that VHT capable devices can interoperate with OFDM devices on the same network by using common features and parameters that are supported by both PHYs. For example, VHT capable devices can use a channel bandwidth of 20 MHz, a modulation scheme of BPSK, QPSK, or 16-QAM, one spatial stream, no beamforming, and OFDM PHY and MAC headers when communicating with OFDM devices. Backward compatibility also means that VHT capable devices can fall back to OFDMmode when the signal quality or SNR is too low for VHT mode. References: 1, Chapter 3, page 123; 2, Section 3.2

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.

References:

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

Understanding 2.4 GHz channel arrangement and interference patterns in 802.11 wireless networks.

Based on the information given, what can be determined as certainly true about this AP is that it has 4 radio chains. A radio chain is a hardware component that consists of an antenna, a radio frequency (RF) amplifier, and a transceiver. The number of radio chains indicates how many spatial streams an AP can transmit or receive simultaneously using Multiple Input Multiple Output (MIMO) technology. The notation x:y:z in an AP specification denotes the number of radio chains (x), the number of spatial streams (y), and the number of spatial streams per band (z). Therefore, a tri-band, 4x4:4, Wi-Fi 6, 802.11ax AP has four radio chains in each of its three bands (2.4 GHz, low 5 GHz, and high 5 GHz). It also supports four spatial streams in total and four spatial streams per band. It cannot be determined as certainly true that it supports four channels in each band, UL-MU-MIMO, or uses a modified OpenWRT firmware based on the information given. References: [CWNP Certified Wireless Network Administrator Official Study Guide: ExamCWNA-109], page 223; [CWNA: Certified Wireless Network Administrator Official Study Guide: ExamCWNA-109], page 213.

The response that you should give to your manager’s suggestion of implementing the security practices of disabling the broadcasting of the SSID in Beacons and configuring the access points not to respond to Probe Request frames that have a null SSID field is that any 802.11 protocol analyzer can see the SSID in clear text in frames other than Beacons frames. This negates any security benefit of trying to hide the SSID in Beacons and Probe Response frames. The SSID (Service Set Identifier) is a human-readable name that identifies a WLAN and allows users to connect to it. The SSID is transmitted in clear text in several types of 802.11 frames, such as Beacon frames, Probe Request frames, Probe Response frames, Association Request frames, Association Response frames, Reassociation Request frames, and Reassociation Response frames. Some people may think that hiding the SSID can improve the security of the WLAN by making it invisible to potential intruders. However, this is not true, as hiding the SSID only removes it from Beacon frames and Probe Response frames that have a null SSID field. The SSID is still present in other types of frames that can be easily captured and analyzed by any 802.11 protocol analyzer or wireless scanner tool. Therefore, hiding the SSID does not provide any real security benefit and may even cause some compatibility and performance issues for legitimate users. References: 1, Chapter 4, page 133; 2, Section 4.1

In addition to coverage analysis results, what should be included in a post-deployment site survey report to ensure WLAN users experience acceptable performance is Capacity 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. References: [CWNP Certified Wireless Network Administrator Official Study Guide: ExamCWNA-109], page 548; [CWNA: Certified Wireless Network Administrator Official Study Guide: ExamCWNA-109], page 518.