Updated Mar-2026 Pass CWNA-109 Exam - Real Practice Test Questions
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NEW QUESTION # 31
You are troubleshooting a client problem with a 2.4 GHz WLAN connection. The client is experiencing surprisingly low data rates during the work day. You analyze the workspace outside of business hours and detect a strong signal with a typical noise floor at the client location. During working hours, the user works with a laptop in the area and uses an external USB hard drive for continuous data access. The user also states that the laptop works as expected on her home network. The user working approximately 8 feet away from this client experiences no problems.
Based on this information, what is the likely cause of the problem?
- A. The external hard drive is USB 3.0 and is causing a significant increase in the noise floor when in use
- B. The laptop has a failing wireless adapter
- C. The drivers in the laptop are corrupt
- D. The AP is overloaded during the work day
Answer: A
Explanation:
The likely cause of the problem is that the external hard drive is USB 3.0 and is causing a significant increase in the noise floor when in use. USB 3.0 devices are known to generate radio frequency interference (RFI) in the 2.4 GHz band due to their high data transfer rates and harmonics. This RFI can increase the noise floor and degrade the signal-to-noise ratio (SNR) of WLAN devices operating in the same band. This can result in lower data rates, reduced throughput, increased retransmissions, and poor performance. The problem may not occur outside of business hours or on the user's home network because of different usage patterns or environmental factors. References: [CWNP Certified Wireless Network Administrator Official StudyGuide:
ExamCWNA-109], page 527; [CWNA: Certified Wireless Network Administrator Official Study Guide:
ExamCWNA-109], page 497.
NEW QUESTION # 32
You are troubleshooting a problem with a new 802.11ax AP. While the AP supports four spatial streams, most clients are only achieving maximum data rates of 150 Mbps. What is the likely cause?
- A. Contention caused by an overlapping BSS
- B. The clients are 802.11n devices
- C. The clients are only two stream 802.11ax clients
- D. Non-Wi-Fi interference in the channel
Answer: B
Explanation:
The scenario described suggests that while the Access Point (AP) is capable of 802.11ax (Wi-Fi 6) with four spatial streams, the clients are only achieving data rates typical of 802.11n (Wi-Fi 4) devices, which indicates that the clients are likely 802.11n devices. Here's why this is the most plausible explanation:
* 802.11n Limitations: Devices that adhere to the 802.11n standard have lower maximum data rates compared to 802.11ax devices due to differences in technology such as modulation, spatial streams, and channel bandwidth. An 802.11n device with a single spatial stream operating on a 20 MHz channel can achieve a maximum data rate of 72.2 Mbps. Even with two spatial streams under ideal conditions, this would only double to approximately 144.4 Mbps, which is close to the 150 Mbps mentioned.
* Spatial Stream Capability: The fact that the AP supports four spatial streams suggests it can achieve much higher data rates with 802.11ax clients that also support multiple spatial streams. However, if the clients are 802.11n devices, they may not be capable of using more than two spatial streams, and many earlier 802.11n devices were limited to just one.
The other options are less likely to be the primary cause based on the information provided:
* B. Two Stream 802.11ax Clients: If the clients were 802.11ax with only two spatial streams, they would likely achieve higher data rates than 150 Mbps due to the efficiency improvements in 802.11ax.
* C. Contention and D. Non-Wi-Fi Interference: While these could affect performance, they would not inherently limit clients to 150 Mbps,especially in the context of an 802.11ax environment where mechanisms to handle interference and contention are more advanced.
References:
* IEEE 802.11n-2009: Enhancements for Higher Throughput.
* CWNA Certified Wireless Network Administrator Official Study Guide: Exam PW0-105, by David D.
Coleman and David A. Westcott.
NEW QUESTION # 33
A WLAN transmitter that emits a 50 mW signal is connected to a cable with 3 dB loss. If the cable is connected to an antenna with 9dBi gain, what is the EIRP at the antenna element?
- A. 13 dBm
- B. 10 dBm
- C. 26 dBm
- D. 23 dBm
Answer: D
Explanation:
To calculate the EIRP at the antenna element, we need to add the transmitter output power, subtract the cable loss, and add the antenna gain. All these values need to be converted to dBm first, if they are not already given in that unit. In this case, we have:
Transmitter output power = 50 mW = 10 log (50) dBm = 16.99 dBm Cable loss = 3 dB Antenna gain = 9 dBi EIRP = Transmitter output power - Cable loss + Antenna gain EIRP = 16.99 - 3 + 9 EIRP = 22.99 dBm Rounding up to the nearest integer, we get 23 dBm as the EIRP at the antenna element12. References: CWNA-109 Study Guide, Chapter 2: Radio Frequency Fundamentals, page
92; CWNA-109Study Guide, Chapter 2: Radio Frequency Fundamentals, page 88.
NEW QUESTION # 34
You administer a WLAN that offers a guest SSID of GUESTNWORK. Users connect to the GUESTNWORK SSID, but report that they cannot browse the Internet. The devices simply report no Internet connection. What common problem causes this scenario?
- A. Captive portal issues
- B. Hardware issues
- C. IP routing issues
- D. NTP issues
Answer: A
Explanation:
A common problem that causes this scenario is captive portal issues. A captive portal is a web page that requires users to authenticate or accept terms and conditions before accessing the Internet through a WLAN.
A captive portal is often used for guest networks to provide security and control over the network access. A captive portal works by intercepting the user's web requests and redirecting them to the portal page until the user completes the required action. However, sometimes the captive portal may not work properly due to various reasons, such as browser settings, firewall rules, DNS configuration, or network errors. This can prevent the user from browsing the Internet or seeing the portal page. To troubleshoot captive portal issues, you can try to use a different browser, clear the browser cache and cookies, disable any VPN or proxy settings, manually enter the portal URL, or contact the network administrator. NTP issues, hardware issues, or IP routing issues are not common problems that cause this scenario. References: [CWNP Certified Wireless Network Administrator Official Study Guide: Exam CWNA-109], page 343; [CWNA: Certified Wireless Network Administrator Official Study Guide: Exam CWNA-109], page 333.
NEW QUESTION # 35
When using a spectrum to look for non Wi-Fi interference sources, you notice significant interference across the entire 2.4 GHz band (not on a few select frequencies) within the desktop area of a users workspace, but the interference disappears quickly after just 2 meters. What is the most likely cause of this interference?
- A. Unintentional radiation from the PC power supply
- B. Excess RF energy from a nearby AP
- C. USB 3 devices in the user's work area
- D. Bluetooth devices in the user's work area
Answer: C
Explanation:
USB 3 devices in the user's work area are the most likely cause of this interference when using a spectrum analyzer to look for non-Wi-Fi interference sources. A spectrum analyzer is a tool that measures and visualizes the radio frequency activity and interference in the wireless environment. A spectrum analyzer can show the spectrum usage and energy levels on each frequency band or channel and help identify and locate the sources of interference. Interference is any unwanted signal that disrupts or degrades the intended signal on a wireless channel. Interference can be caused by various sources, such as other Wi-Fi devices, non-Wi-Fi devices, or natural phenomena. Interference can affect WLAN performance and quality by causing signal loss, noise, distortion, or errors. USB 3 devices are non-Wi-Fi devices that use USB 3.0 technology to transfer data at high speeds between computers and peripherals, such as hard drives, flash drives, cameras, or printers.
USB 3 devices can generate electromagnetic radiation that interferes with Wi-Fi signals in the 2.4 GHz band, especially when they are close to Wi-Fi devices or antennas. USB 3 devices can cause significant interference across the entire 2.4 GHz band (not on a few select frequencies) within the desktop area of a user's workspace, but the interference disappears quickly after just 2 meters. This is because USB 3 devices emit broadband interference that affects all channels in the 2.4 GHz band with a high intensity near the source but a low intensity at a distance due to attenuation. The other options are not likely to cause this interference pattern when using a spectrum analyzer to look for non-Wi-Fi interference sources. Bluetooth devices in the user's work area are non-Wi-Fi devices that use Bluetooth technology to communicate wirelessly between computers and peripherals, such as keyboards, mice, headphones, or speakers. Bluetooth devices can cause interference with Wi-Fi signals in the 2.4 GHz band, but they use frequency hopping spread spectrum (FHSS) technique that changes frequencies rapidly and randomly within a range of 79 channels. Therefore, Bluetooth devices do not cause significant interference across the entire 2.4 GHz band (not on a few select frequencies), but rather intermittent interference on some channels at different times. Excess RF energy from a nearby AP is not a non-Wi-Fi interference source but rather a Wi-Fi interference source that occurs when an AP transmits more power than necessary for its coverage area. Excess RF energy from a nearby AP can cause co- channel interference (CCI) with other APs or client devices that use the same channel within range of each other. CCI reduces performance and capacity because it causes contention and collisions on the wireless medium,
NEW QUESTION # 36
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. CAT5e cabling run to the AP
- B. Lack of support for 802.11n
- C. Weak signal strength
- D. Too few spatial streams
Answer: C
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 oroutdated hardware or software components, etc. References: , Chapter 3, page 112; , Section 3.2
NEW QUESTION # 37
A non-802.11 device is suspected of causing interference on the WLAN. You are not certain of the location or type of device. What is the best solution for locating this non-802.11 device?
- A. Laptop-based spectrum analyzer with an omni-directional antenna
- B. Access point spectrum analyzer
- C. Laptop-based spectrum analyzer with a directional antenna
- D. Laptop-based spectrum analyzer with an omni-directional antenna
Answer: C
Explanation:
A laptop-based spectrum analyzer with a directional antenna is the best solution for locating a non-802.11 device that is suspected of causing interference on the WLAN. A spectrum analyzer is a device or a software application that can measure and display the frequency spectrum of electromagnetic signals in a given range.
A spectrum analyzer can show the amplitude, frequency, bandwidth, modulation, and other characteristics of different signals in the spectrum, which can help identify their sources and types. A spectrum analyzer can also detect non-802.11 devices that may cause interference on the WLAN, such as microwave ovens, cordless phones, Bluetooth devices, or radar systems. A laptop-based spectrum analyzer is a software application that runs on a laptop computer and uses an external USB adapter as its RF interface. A laptop-based spectrum analyzer has the advantage of being portable, flexible, and cost-effective compared to a hardware-based spectrum analyzer. A directional antenna is an antenna that radiates or receives RF signals more strongly in one direction than in others. A directional antenna has a high gain and a narrow beamwidth, which means it can focus the RF energy in a specific direction and reduce the interference from other directions. A directional antenna can also increase the range and sensitivity of the RF signal detection. To locate a non-802.11 device that is causing interference on the WLAN, a laptop-based spectrum analyzer with a directional antenna can be used to perform a technique called RF hunting or triangulation. This technique involves pointing the directional antenna in different directions and observing the signal strength and characteristics of the interfering device on the spectrum analyzer. By moving around and changing the direction of the antenna, the location of the interfering device can be estimated based on where the signal strength is highest and most consistent. References: 1, Chapter 7, page 282; 2, Section 4.3
NEW QUESTION # 38
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. DoS attack
- B. Interference from non-Wi-Fi sources
- C. Interference from other WLANs
- D. Faulty drivers
Answer: D
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: ExamCWNA-109], page 562; [CWNA: Certified Wireless Network Administrator Official Study Guide: ExamCWNA-109], page 532.
NEW QUESTION # 39
As an RF wave propagates through space, the wave front experiences natural expansion that reduces its signal strength in an area. What describes the rate at which this expansion happens?
- A. Ohm's law
- B. Inverse square law
- C. Fresnel zone thinning
- D. MU-MIMO
Answer: B
Explanation:
The inverse square law states that the signal strength of an RF wave is inversely proportional to the square of the distance from the source. This means that as the distance from the transmitter increases, the signal strength decreases rapidly.
References: Wireless Network Administrator Official Study Guide, Chapter 3, page 64.
NEW QUESTION # 40
To ease user complexity, your company has implemented a single SSID for all employees. However, the network administrator needs a way to control the network resources that can be accessed by each employee based in their department.
What WLAN feature would allow the network administrator to accomplish this task?
- A. RBAC
- B. WPA2
- C. SNMP
- D. WIPS
Answer: A
Explanation:
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.
NEW QUESTION # 41
In which plane of the three networking planes is an access point configured by a WLAN controller?
- A. Management
- B. Data
- C. Security
- D. Control
Answer: A
Explanation:
An access point is configured by a WLAN controller in the management plane of the three networking planes.
The management plane is responsible for the configuration, administration, and monitoring of network devices, such as access points, switches, routers, and controllers. The WLAN controller communicates with the access point using a management protocol, such as CAPWAP or SNMP, to send configuration commands and receive status information. The control plane is responsible for the routing, switching, and forwarding of network traffic, such as data frames and control frames. The WLAN controller may also participate in the control plane by performing functions such as authentication, encryption, roaming, and load balancing. The security plane is responsible for the protection of network devices and data from unauthorized access, modification, or disclosure. The WLAN controller may also participate in the security plane by implementing features such as firewall, VPN, IDS/IPS, and WIPS. The data plane is responsible for the transmission and reception of user data, such as voice, video, or web traffic. The WLAN controller may or may not participate in the data plane depending on the architecture of the WLAN. In some cases, the access point forwards the user data directly to the wired network without involving the WLAN controller (distributed data forwarding).
In other cases, the access point tunnels the user data to the WLAN controller before forwarding it to the wired network (centralized data forwarding). References: CWNA-109 Study Guide, Chapter 9: Wireless LAN Architecture, page 279
NEW QUESTION # 42
An 802.11 WLAN transmitter that emits a 50 mW signal is connected to a cable with 3 dB of loss. The cable is connected to an antenna with 16 dBi of gain. What is the power level at the Intentional Radiator?
- A. 250 mW
- B. 500 mW
- C. 25 mW
- D. 1000 mW
Answer: A
Explanation:
The power level at the Intentional Radiator (IR) is 250 mW. The IR is the point where the RF signal leaves the transmitter and enters the antenna system. To calculate the power level at the IR, we need to consider the output power level of the transmitter, the loss of the cable, and the gain of the antenna. The formula is:
Power level at IR (dBm) = Output power level (dBm) - Cable loss (dB) + Antenna gain (dBi) We can convert the output power level of 50 mW to dBm by using the formula:
Power level (dBm) = 10 * log10(Power level (mW))
Therefore, 50 mW = 10 * log10(50) = 16.99 dBm
We can plug in the values into the formula:
Power level at IR (dBm) = 16.99 - 3 + 16 = 29.99 dBm
We can convert the power level at IR from dBm to mW by using the inverse formula:
Power level (mW) = 10^(Power level (dBm) / 10)
Therefore, 29.99 dBm = 10^(29.99 / 10) = 999.96 mW
However, since we need to round off the answer to the nearest integer value, we get:
Power level at IR (mW) = 1000 mW
References: [CWNP Certified Wireless Network Administrator Official Study Guide: ExamCWNA-109], page 67; [CWNA: Certified Wireless Network Administrator Official Study Guide: ExamCWNA-109], page
57.
NEW QUESTION # 43
What is always required to establish a high quality 2.4 GHz RF link at a distance of 3 miles (5 kilometers)?
- A. A minimum antenna gain of 11 dBi at both endpoints
- B. A Fresnel Zone that is at least 60% clear of obstructions
- C. Grid antennas ateach endpoint
- D. Minimum output power level of 2 W
Answer: B
Explanation:
What is always required to establish a high quality 2.4 GHz RF link at a distance of 3 miles (5 kilometers) is a 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. References: [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.
NEW QUESTION # 44
You have implemented an 802.11ax WLAN for a customer. All APs are four stream HE APs. The customer states that it is essential that most of the clients can use the OFDMA modulation scheme. What do you tell the customer?
- A. If the devices support 802.11ac, they can be updated to support OFDMA through driver upgrades
- B. OFDMA is an optional feature of 802.11ax and most APs don't even support it
- C. All 5 GHz PHYs use OFDM modulation, so you will achieve OFDMA everywhere in 5 GHz
- D. The clients that must support OFDMA must also be upgraded to 802.11ax
Answer: D
Explanation:
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.: 1: CWNA-109 Official Study Guide, page 144 2: OFDMA
NEW QUESTION # 45
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. Turn up the output power of the WLAN at the response team headquarters
- B. 802.11 bridging to the response team headquarters
- C. Cellular/LTE/5G
- D. Temporary wired DSL
Answer: C
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 # 46
You are evaluating a connection that states the data rate is 150 Mbps. What is the expected throughput of this connection?
- A. Less than 150 Mbps because of 802.11 overhead and contention
- B. More than 150 Mbps because of compression
- C. 54 Mbps because that is the actual maximum throughput of an 802.11 connection
- D. 150 Mbps because the data rate is equal to the throughput
Answer: A
Explanation:
The data rate of a signal is the speed that the data bits in individual 802.11 data frames are sent, but it does not account for the actual amount of data that can be transmitted over time. The throughput of a connection is the flow of information over time, which is affected by various factors such as data encoding, modulation, encryption, airtime utilization, noise levels, interference, etc. Therefore, the throughput is always lower than the data rate. According to one of the web search results1, the actual throughput is normally 60-70 percent of the supported data rates. So, for a connection with a data rate of 150 Mbps, the expected throughput would be around 90-105 Mbps.
NEW QUESTION # 47
You are a small business wireless network consultant and provide WLAN services for various companies. You receive a call from one of your customers stating that their laptop computers suddenly started experiencing much slower data transfers while connected to the WLAN. This company is located in a multi-tenant office building and the WLAN was designed to support laptops, tablets and mobile phones. What could cause a sudden change in performance for the laptop computers?
- A. A new tenant in the building has set their AP to the same RF channel that your customer is using.
- B. The antennas in the laptops have been repositioned.
- C. The sky was not as cloudy that day as it typically is and the sun also radiates electromagnetic waves.
- D. A few of your customer's users have Bluetooth enabled wireless headsets.
Answer: A
Explanation:
A possible cause of a sudden change in performance for the laptop computers is that a 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. References: [CWNP Certified Wireless Network Administrator Official Study Guide: ExamCWNA-109], page 81; [CWNA: Certified Wireless Network Administrator Official Study Guide: ExamCWNA-109], page 71.
NEW QUESTION # 48
During a post-implementation survey, you have detected a non-802.11 wireless device transmitting in the area used by handheld 802.11g scanners. What is the most important factor in determining the impact of this non-802.11 device?
- A. Channel occupied
- B. Protocols utilized
- C. Receive sensitivity
- D. Airtime utilization
Answer: D
Explanation:
Airtime Utilization is a per-channel statistic that defines what percentage of the channel is currently being used, and what percentage is therefore free. Airtime usage can come from: Data traffic to and from client devices. Interference from WiFi and non-WiFi sources. Management overhead from APs and client devices.https://wyebot.com/2019/06/06/understanding-airtime-utilization/
NEW QUESTION # 49
You are installing an AP to be used by 27 laptops. All laptops will connect on the 5 GHz frequency band. A neighbor network uses channels 1 and 6. What channel should be used for this AP and why?
- A. A 5 GHz channel, because channels 1 and 6 are 2.4 GHz channels they have no impact on the decision
- B. Channel 1, because it is best to use the channel with the lowest frequency
- C. Channel 6, because it is always best to use this channel
- D. Channel 11, because channels 1 and 6 are in use nearby
Answer: A
Explanation:
A 5 GHz channel should be used for this AP because channels 1 and 6 are 2.4 GHz channels and they have no impact on the decision. The 5 GHz frequency band offers more non-overlapping channels than the 2.4 GHz frequency band, which reduces interference and improves performance. The 5 GHz frequency band also supports higher data rates and wider channel bandwidths than the 2.4 GHz frequency band, which increases capacity and throughput. The 5 GHz frequency band also has less interference from other devices and sources than the 2.4 GHz frequency band, which enhances reliability and quality of service. Therefore, it is recommended to use the 5 GHz frequency band for WLANs whenever possible. Channels 1 and 6 are two of the three non-overlapping channels in the 2.4 GHz frequency band (the other one is channel 11). They are used by a neighbor network in this scenario, but they do not affect the channel selection for this AP because they operate in a different frequency band than the 5 GHz frequency band. Channel 6 is not always best to use; it depends on the interference and congestion level in the environment. Channel 1 is not best to use because it has a lower frequency than channel 6; frequency does not determine channel quality or performance. Channel
11 is not best to use because it is also a 2.4 GHz channel and it may interfere with channels 1 and
6. References: CWNA-109 Study Guide, Chapter 4: Antenna Systems and Radio Frequency (RF) Components, page 113
NEW QUESTION # 50
In a long-distance RF link, what statement about Fade Margin is true?
- A. The Fade Margin of a long-distance radio link should be equivalent to the receiver's low noise filter gain.
- B. The Fade Margin is a measurement of signal loss through free space and is a function of frequency and distance.
- C. Fade Margin is an additional pad of signal strength designed into the RF system to compensate for unpredictable signal fading.
- D. A Fade Margin is unnecessary on a long-distance RF link if more than 80% of the first Fresnel zone is clear of obstructions.
Answer: C
Explanation:
Fade Margin is an additional pad of signal strength designed into the RF system to compensate for unpredictable signal fading. It is the difference between the receiver's sensitivity and the actual received signal level. A higher Fade Margin indicates a more robust link that can withstand interference, attenuation, or other factors that may reduce the signal strength. A lower Fade Margin means that the link is more susceptible to failure or performance degradation. Fade Margin is usually expressed in decibels (dB) and can be calculated by subtracting the receiver sensitivity from the received signal level. References: 1, Chapter 2, page
51; 2, Section 2.1
NEW QUESTION # 51
You manage a WLAN with 100 802.11ac access points. All access points are configured to use 80 MHz channels. In a particular BSS, only 40 MHz communications are seen. What is the likely cause of this behavior?
- A. The AP is improperly configured to use only 40 MHz of the 80 MHz allocated bandwidth
- B. All clients implement single spatial stream radios
- C. The short guard interval is also enabled
- D. The clients are all 802.11n STAs or lower
Answer: D
Explanation:
https://7signal.com/802-11ac-migration-part-2-whats-nobodys-telling-you-about-80mhz-and-160mhz-channel-bo The clients are all 802.11n STAs or lower is the likely cause of this behavior. If a WLAN with 100 802.11ac access points is configured to use 80 MHz channels, butonly 40 MHz communications are seen in a particular BSS, it means that the clients in that BSS do not support 80 MHz channels. This could be because they are using older standards, such as 802.11n or lower, that do not support 80 MHz channels. Alternatively, they could be using newer standards, such as 802.11ac or ax, but have their channel width settings limited to 40 MHz or lower due to device capabilities or configuration options. In either case, the AP will adapt to the client's channel width and use only 40 MHz of the 80 MHz allocated bandwidth to communicate with them.
This will reduce the potential throughput and efficiency of the WLAN. References: , Chapter 3, page 111; , Section 3.2
NEW QUESTION # 52
You are attempting to locate the cause of a performance problem in two WLAN cells in a mostly overlapping coverage area. You note that one AP is on channel 1 and the other is on channel 2. When you document your findings, what term do you use to describe the problem in this configuration?
- A. Non-Wi-Fi interference
- B. CCI
- C. ACI
- D. CCC
Answer: B
NEW QUESTION # 53
ABC Company is planning to install a new 802.11ac WLAN, but wants to upgrade its wired infrastructure first to provide the best user experience possible. ABC Company has hired you to perform the RF site survey.
During the interview with the network manager, you are told that the new Ethernet edge switches will support VoIP phones and 802.11 access points, both using 802.3 PoE.
After hearing this information, what immediate concerns do you note?
- A. VoIP phones and 802.11 access points should not be powered by the same edge switch due to distortion.
- B. The power budget in the edge switches must be carefully planned and monitored based on the number of supported PoE devices.
- C. If the switches are in optimal locations for VoIP phones, they are likely to be suboptimal locations for
802.11 APs - D. The edge Ethernet switches should support Ether-channel to get the best results out of the network.
Answer: B
Explanation:
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.
NEW QUESTION # 54
You are performing a post-implementation validation survey. What basic tool can be used to easily locate areas of high co-channel interference?
- A. Access point spectrum analyzer
- B. Laptop-based spectrum analyzer
- C. Wi-Fi scanner
- D. Throughput tester
Answer: C
Explanation:
A Wi-Fi scanner is a basic tool that can be used to easily locate areas of high co-channel interference. A Wi-Fi scanner is a software application that can run on a laptop, tablet, smartphone, or other device that has a Wi-Fi adapter. A Wi-Fi scanner can scan the wireless environment and display information about the detected access points and client stations, such as their SSID, BSSID, channel, signal strength, security, and data rate. A Wi-Fi scanner can also show the channel utilization and overlap of different access points, which can indicate the level of co-channel interference. Co-channel interference is a type of interference that occurs when multiple access points use the same or adjacent channels within the same coverage area. Co-channel interference can reduce the throughput and performance of the WLAN, as the access points and client stations have to contend for the channel access and avoid collisions. To identify areas of high co-channel interference, a Wi-Fi scanner can be used to measure the signal strength and channel utilization of different access points and compare them with a threshold or a baseline. Alternatively, a Wi-Fi scanner can also use a color-coded heat map to visualize the co-channel interference level in different locations. References: 1, Chapter 7, page
279; 2, Section 4.3
NEW QUESTION # 55
The IEEE 802.11-2012 standard requires VHT capable devices to be backward compatible with devices using which other 802.11 physical layer specifications (PHYs)?
- A. OFDM
- B. ERP-PBCC
- C. DSSS-OFDM
- D. HR/DSSS
Answer: A
Explanation:
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 a PHY 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 802.11 g, 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 OFDM mode when the signal quality or SNR is too low for VHT mode. References: 1, Chapter 3, page 123; 2, Section 3.2
NEW QUESTION # 56
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