[2023] CWNA-108 by CWNA Certification Actual Free Exam Practice Test
Free CWNA Certification CWNA-108 Exam Question
NEW QUESTION # 13
A client complains of low data rates on his computer. When you evaluate the situation, you see that the signal strength is -84 dBm and the noise floor is -96 dBm. The client is an 802.11ac client and connects to an
802.11ac AP. Both the client and AP are 2x2:2 devices. What is the likely cause of the low data rate issue?
- A. Weak signal strength
- B. CAT5e cabling run to the AP
- C. Too few spatial streams
- D. Lack of support for 802.11n
Answer: A
Explanation:
Explanation
Weak signal strength is the likely cause of the low data rate issue for the client that has a signal strength of -84 dBm and a noise floor of -96 dBm. The client is an 802.11ac client and connects to an 802.11ac AP. Both the client and AP are 2x2:2 devices. Signal strength is the measure of how strong the RF signal is at the receiver.
Signal strength can affect the reliability and performance of the wireless connection, as well as the data rate and throughput of the traffic. The higher the signal strength, the better the signal quality and the higher the data rate. The lower the signal strength, the worse the signal quality and the lower the data rate.
The data rate of an 802.11ac connection depends on several factors, such as channel bandwidth, modulation and coding scheme (MCS), spatial streams, guard interval, and beamforming. However, these factors are also influenced by the signal strength, as they require a certain signal-to-noise ratio (SNR) to operate properly.
SNR is the ratio of the signal strength to the noise floor, which is the measure of the background noise or interference in the RF environment. The higher the SNR, the more robust and efficient the communication.
The lower the SNR, the more prone and vulnerable to errors and retries.
According to the CWNA Official Study Guide , Table 3.7, page 112, an 802.11ac connection with a channel bandwidth of 80 MHz, an MCS of 9, two spatial streams, a short guard interval, and no beamforming can achieve a maximum data rate of 867 Mbps. However, this data rate requires a minimum SNR of 30 dB to maintain a sufficient signal quality. If the signal strength is -84 dBm and the noise floor is -96 dBm, then the SNR is only 12 dB (-84 dBm - (-96 dBm) = 12 dB), which is far below the required SNR for this data rate.
Therefore, the data rate will drop significantly to match the lower SNR and signal quality.
To solve this problem, the signal strength should be increased to improve the SNR and data rate. This can be done by adjusting the output power or channel assignment of the AP or client, relocating or reorienting some APs or antennas to reduce attenuation or interference, updating or replacing some faulty or outdated hardware or software components, etc. References: , Chapter 3, page 112; , Section 3.2
NEW QUESTION # 14
In an 802.11 2.4 GHz system, what 22 MHz channels are considered non-overlapping?
- A. 4 and 6
- B. 1 and 5
- C. 2 and 8
- D. 7 and 11
Answer: B
Explanation:
Explanation
In an 802.11 2.4 GHz system, channels 1 and 5 are considered non-overlapping. In the 2.4 GHz band, there are
14 channels defined by the IEEE 802.11 standard, but only 11 of them are available in North America and most other regions. Each channel has a bandwidth of 22 MHz, but they are spaced only 5 MHz apart from each other. This means that adjacent channels overlap with each other and cause interference. To avoid interference, it is recommended to use only non-overlapping channels, which are channels that do not share any frequency range with each other. In the 2.4 GHz band, there are only three non-overlapping channels:
channel 1, channel 6, and channel 11. However, some devices can use channel bonding to combine two adjacent channels into one wider channel of 40 MHz, which can provide higher throughput but also more interference. In this case, there are only two non-overlapping channels: channel 1+5 and channel
6+10. References: 1, Chapter 3, page 86; 2, Section 3.2
NEW QUESTION # 15
In addition to coverage analysis results, what should be included in a post-deployment site survey report to ensure WLAN users experience acceptable performance?
- A. Layer 4 protocol availability analysis results
- B. Application Layer protocol availability analysis results
- C. Capacity analysis results
- D. WAN interface analysis results
Answer: C
NEW QUESTION # 16
What statement is true concerning the use of Orthogonal Frequency Division Multiplexing (OFDM) modulation method in IEEE 802.11 WLANs?
- A. OFDM modulation is used only in 5 GHz 802. 11 transmissions.
- B. OFDM implements BPSK modulation to allow for data rates up to 7 Gbps.
- C. OFDM was used by Frequency Hopping Spread Spectrum (FHSS) PHY devices.
- D. OFDM was first introduced in 802. 11a and is used by the ERP, HT and VHT PHYs as well
Answer: A
NEW QUESTION # 17
A natural disaster has occurred in a remote area that is approximately 57 miles from the response team headquarters. The response team must implement a local wireless network using 802.11 WLAN access points.
What is the best method, of those listed, for implementation of a network back-haul for communications across the Internet in this scenario?
- A. 802.11 bridging to the response team headquarters
- B. Turn up the output power of the WLAN at the response team headquarters
- C. Cellular/LTE/5G
- D. Temporary wired DSL
Answer: C
Explanation:
Explanation
Cellular/LTE/5G is the best method for implementing a network backhaul for communications across the Internet in a remote area that is affected by a natural disaster. This is because cellular/LTE/5G networks are wireless and do not depend on physical infrastructure that may be damaged or unavailable in such scenarios.
Cellular/LTE/5G networks also offer high-speed data transmission and wide coverage area, which are essential for emergency response operations. 802.11 bridging to the response team headquarters is not feasible because it requires line-of-sight and has limited range. Turning up the output power of the WLAN at the response team headquarters is not effective because it may cause interference and does not guarantee reliable connectivity. Temporary wired DSL is not practical because it requires installing cables and equipment that may not be available or accessible in a remote area. References: CWNA-109 Study Guide, Chapter 7: Wireless LAN Topologies, page 2031
NEW QUESTION # 18
When replacing the antenna of a WLAN device with a similar antenna type that has a higher passive gain, what antenna characteristic will decrease?
- A. Beamwidth
- B. Range
- C. Active gain
- D. Receive sensitivity
Answer: A
NEW QUESTION # 19
What factor does not influence the distance at which an RF signal can be effectively received?
- A. Free Space Path Loss
- B. Transmitting station's output power
- C. Receiving station's radio sensitivity
- D. Receiving station's output power
Answer: C
NEW QUESTION # 20
XYZ Company has decided to install an 802.11 WLAN system that will support 1000 wireless users, but they are concerned about network security. XYZ is interested in deploying standardized security features. In addition to WPA2-Enterprise with PEAP and role-based access control, XYZ would like to support management frame protection as well as a fast secure roaming protocol for future mobile handsets.
As XYZ Company selects a product to deploy, what two IEEE amendments, which are included in
802.11- 2016, should be supported to provide the management frame protection and fast secure roaming security features?
- A. 802.11r and 802.11k
- B. 802.11z and 802.11w
- C. 802.11j and 802.11k
- D. 802.11r and 802.11w
Answer: D
NEW QUESTION # 21
You are attempting to explain RF shadow and how it can cause lack of coverage. What common building item frequently causes RF shadow and must be accounted for in coverage plans?
- A. Carpeted floors
- B. Cubicle partitions
- C. Elevators
- D. Wooden doors
Answer: B
NEW QUESTION # 22
The requirements for a WLAN you are installing state that it must support unidirectional delays of less than
150 ms and the signal strength at all receivers can be no lower than -67 dBm. What application is likely used that demands these requirements?
- A. RTLS
- B. FTP
- C. VoIP
- D. E-Mail
Answer: C
NEW QUESTION # 23
What phrase defines Equivalent Isotropically Radiated Power (EIRP)?
- A. Power supplied from the transmission line to the antenna input
- B. The power output from the radio into the RF cable
- C. The power output from the radio after cable losses
- D. The highest RF signal strength that is transmitted from a given antenna
- E. Reflected power due to an impedance mismatch in the signal path
Answer: D
NEW QUESTION # 24
In addition to coverage analysis results, what should be included in a post-deployment site survey report to ensure WLAN users experience acceptable performance?
- A. Layer 4 protocol availability analysis results
- B. Application Layer protocol availability analysis results
- C. Capacity analysis results
- D. WAN interface analysis results
Answer: C
Explanation:
Explanation
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: Exam CWNA-107], page 548; [CWNA: Certified Wireless Network Administrator Official Study Guide: Exam CWNA-106], page 518.
NEW QUESTION # 25
You are deploying a WLAN with the access points configured for 10 mW of output power on the 2.4 GHz radios and 20 mW of output power on the 5GHz radios. Some semi-directional antennas are also in use. What kind of deployment is described?
- A. SOHO
- B. Residential
- C. Standard office
- D. High density
Answer: A
NEW QUESTION # 26
You recently purchased four laptops containing dual-band 802.11ac adapters. The laptops can connect to your
2.4 GHz network, but they cannot connect to the 5 GHz network. The laptops do not show the 5 GHz SSIds, which are different than the 2.4 GHz SSIDs. Existing devices can connect to the 5 GHz SSIDs with no difficulty. What is the likely problem?
- A. Interference from non-Wi-Fi sources
- B. DoS attack
- C. Faulty drivers
- D. Interference from other WLANs
Answer: C
Explanation:
Explanation
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: Exam CWNA-107], page 562; [CWNA: Certified Wireless Network Administrator Official Study Guide: Exam CWNA-106], page 532.
NEW QUESTION # 27
You are troubleshooting a client issue on a Windows laptop. The laptop can see and connect to 2.4 GHz APs, but is does not even see 5 GHz APs. While evaluating the issue, you determine that this problem is happening for all of the laptops of this model in the organization. Several other tablets connect on channel 48 and channel
52 in the same work areas. What is the likely problem?
- A. The access points are configured to disallow 5 GHz.
- B. The antennas in the laptop have insufficient gain to detect the 5 GHz signals.
- C. The clients are configured to use WPA and 5 GHz channels only support WPA2.
- D. The client drivers are faulty and should be upgraded.
Answer: B
Explanation:
Explanation/Reference:
NEW QUESTION # 28
You were previously onsite at XYZ's facility to conduct a pre-deployment RF site survey. The WLAN has been deployed according to your recommendations and you are onsite again to perform a post-deployment validation survey.
When performing this type of post-deployment RF site survey voice over Wi-Fi, what is an action that must be performed?
- A. Spectrum analysis to locate and identify RF interference sources.
- B. Frequency-band hopping analysis to detect improper RF channel implementations.
- C. Protocol analysis to discover channel use on neighboring APs.
- D. Application analysis with an active phone call on an VoWiFi handset.
Answer: D
Explanation:
Explanation
When performing a post-deployment validation survey for voice over Wi-Fi (VoWiFi), an action that must be performed is Application analysis with an active phone call on a VoWiFi handset. Application analysis is a method of testing the performance of a specific application over the WLAN by measuring parameters such as throughput, latency, jitter, packet loss, MOS score, and R-value. Application analysis with an active phone call on a VoWiFi handset can help to evaluate the quality of service (QoS) and user experience of VoWiFi calls over the WLAN. It can also help to identify any issues or bottlenecks that may affect VoWiFi calls such as interference, roaming delays, or insufficient coverage. References: [CWNP Certified Wireless Network Administrator Official Study Guide: Exam CWNA-107], page 549; [CWNA: Certified Wireless Network Administrator Official Study Guide: Exam CWNA-106], page 519.
NEW QUESTION # 29
What statement about the IEEE 802.11-2016 QoS facility is true?
- A. Four 802.1p user priorities are mapped to eight 802.11 transmit queues.
- B. 802.11 control frames are assigned to the 802.11 EF priority queue.
- C. 802.11 QoS is achieved by giving high priority queues a statistical advantage at winning contention.
- D. When the Voice queue has frames awaiting transmission, no data will be transmitted from the Best Effort queue.
Answer: C
Explanation:
Explanation
802.11 QoS is achieved by giving high priority queues a statistical advantage at winning contention. 802.11 QoS is based on the Enhanced Distributed Channel Access (EDCA) mechanism, which defines four access categories (ACs) for different types of traffic: Voice, Video, Best Effort, and Background. Each AC has its own transmit queue and contention parameters, such as Arbitration Interframe Space (AIFS), Contention Window (CW), and Transmission Opportunity (TXOP). These parameters determine how long a station has to wait before transmitting a frame and how long it can occupy the channel. Higher priority ACs have shorter AIFS, smaller CW, and longer TXOP, which means they have more chances to access the channel and send more data than lower priority ACs. However, this does not guarantee that higher priority ACs will always win the contention, as there is still a random backoff process involved. Therefore, 802.11 QoS is a statistical service that provides different levels of service quality based on traffic categories. References: , Chapter 10, page 403; , Section 6.1
NEW QUESTION # 30
You are troubleshooting a controller-based AP that is unable to locate the controller. DHCP is not use and the controller is located at 10.10.10.81/24 while the AP is on the 10.10.16.0/24 network. What should be inspected to verify proper configuration?
- A. NTP
- B. BOOTP
- C. DBS
- D. AP hosts file
Answer: D
NEW QUESTION # 31
What factors will have the most significant impact on the amount of wireless bandwidth available to each station within a BSS?
- A. The layer 3 protocol used by each station to transmit data over the wireless link
- B. The presence of co-located (10m away) access points on non-overlapping channels
- C. The power management settings in the access point's beacons
- D. The number of client stations associated to the BSS
Answer: D
NEW QUESTION # 32
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