Ultimate Guide to Prepare Free CWNP CWNA-109 Exam Questions and Answer
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NEW QUESTION # 30
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. 23 dBm
- B. 10 dBm
- C. 13 dBm
- D. 26 dBm
Answer: A
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 # 31
A wireless engineer is troubleshooting an area where far-away clients associated with an AP experience poor performance because a nearby client is transmitting at a much higher signal level, effectively drowning out the weaker signal at the receiver. What is this condition called?
- A. Hidden node problem
- B. Co-channel interference
- C. Near/far problem
- D. Adjacent channel interference
Answer: C
NEW QUESTION # 32
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. 23 dBm
- B. 10 dBm
- C. 13 dBm
- D. 26 dBm
Answer: A
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 element.
NEW QUESTION # 33
What 802.11 network configuration would result in multiple stations broadcasting Beacon frames with the same BSSID but with different source addresses?
- A. An SCA network is in use.
- B. An IBSS is used instead of a BSS.
- C. Multiple APs have been loaded with the same configuration from an image file.
- D. A single AP supports multiple BSSs with different SSIDs.
Answer: B
Explanation:
An IBSS is used instead of a BSS is a network configuration that would result in multiple stations broadcasting Beacon frames with the same BSSID but with different source addresses. An IBSS (Independent Basic Service Set) is a type of WLAN that does not use an AP but rather allows stations to communicate directly with each other in a peer-to-peer manner. An IBSS is also known as an ad-hoc network or a peer-to-peer network. In an IBSS, each station generates its own Beacon frames to announce its presence and capabilities to other stations within range. The Beacon frames have the same BSSID, which is randomly generated by one of the stations when creating the IBSS, but they have different source addresses, which are the MAC addresses of each station's radio interface. The BSSID is used to identify the IBSS and prevent stations from joining other IBSSs with different BSSIDs. References: , Chapter 1, page 25; , Section 1.1
NEW QUESTION # 34
You administer a small WLAN with nine access point. As a small business, you do not rum a RADIUS server and use WPA2-Personal for security. Recently, you changed the passphrase for WPA2-personal in all Aps and clients. Several users are now reporting the inability to connect to the network at time and it is constrained to one area of the building. When using scanner, you see that the AP covering that area is online
- A. The AP that covers the problem area has failed
- B. The AP that covers the problem area is improperly configured
- C. The clients are improperly configured
- D. The AP that covers the problem area requires a firmware update
Answer: C
Explanation:
This is because the passphrase for WPA2-Personal is case-sensitive and must match exactly on both the AP and the client. If the passphrase is entered incorrectly on the client, the client will not be able to authenticate with the AP and connect to the network. The AP that covers the problem area is not likely to require a firmware update, fail, or be improperly configured, as it is online and works with other clients that have the correct passphrase. To troubleshoot this issue, you can check the passphrase settings on the clients and make sure they matchwith the AP. You can also try to reconnect the clients to the network or reboot them if necessary. For more information on how to configure WPA2-Personal on your router
NEW QUESTION # 35
An RF signal sometimes bends as it passes through a material rather than around an obstacle. What is the RF behavior that this statement best describes?
- A. Reflection
- B. Scattering
- C. Diffraction
- D. Refraction
Answer: D
Explanation:
Refraction is the bending of an RF signal as it passes through a material of different density. Refraction can cause the signal to change its direction and angle of arrival. For example, when a light beam passes from air to water, it bends because of the difference in the refractive index of the two mediums. Similarly, when an RF signal passes from one medium to another, such as from air to glass, it can bend due to the change in the dielectric constant of the materials12. References: 1:CWNA-109Official Study Guide, page 67 2: Refraction
NEW QUESTION # 36
A wireless engineer measures a high VSWR value on an antenna cable run. What does this indicate?
- A. The antenna has excessive gain.
- B. There is a significant impedance mismatch causing signal reflection.
- C. The cable length is too short.
- D. The transmitter power is set too low.
Answer: B
Explanation:
Voltage Standing Wave Ratio (VSWR) is a measurement used to determine how efficiently RF power is transmitted from a source, through a transmission line, to a load such as an antenna. A high VSWR value indicates a significant impedance mismatch somewhere in the RF path, which causes a portion of the signal to be reflected back toward the transmitter instead of being radiated. This reflected energy can reduce range and, in extreme cases, damage the transmitter.
An ideal VSWR value is close to 1:1, indicating minimal reflection.
NEW QUESTION # 37
A WLAN is implemented using wireless controllers. The APs must locate the controllers when powered on and connected to the network. Which one of the following methods is commonly used to locate the controllers by the APs?
- A. SNMP
- B. DHCP
- C. GRE
- D. NTP
Answer: B
Explanation:
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.
NEW QUESTION # 38
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 802.11 ac AP. Both the client and AP are 2x2:2 devices. What is the likely cause of the low data rate issue?
- A. Lack of support for 802.11n
- B. Weak signal strength
- C. Too few spatial streams
- D. CAT5e cabling run to the AP
Answer: B
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 # 39
What is the key difference between a passive and an active manual site survey?
- A. A passive survey only listens for beacon frames without associating, while an active survey associates with each AP and measures actual throughput.
- B. A passive survey requires the surveyor to associate with each AP, while an active survey only listens for beacon frames.
- C. A passive survey can only be performed outdoors.
- D. There is no difference; the terms are interchangeable.
Answer: A
Explanation:
In a passive site survey, the survey software listens for beacon frames from nearby APs to measure signal strength and coverage without actually associating with any of them. In an active site survey, the surveyor's device associates with each AP in turn and can measure actual throughput, retransmissions, and other performance metrics under real association conditions.
Active surveys provide more accurate real-world performance data but take longer to conduct than passive surveys.
NEW QUESTION # 40
What can cause excessive VSWR in RF cables used to connect a radio to an antenna?
- A. Impedance mismatch
- B. High gain yagi antenna
- C. High gain parabolic dish antenna
- D. Radio output power above 100 mW but below 400 mw
Answer: A
Explanation:
Impedance is the measure of opposition to the flow of alternating current (AC) in a circuit. Impedance mismatch occurs when the impedance of the radio does not match the impedance of the antenna or the cable.
This causes some of the transmitted or received signal to be reflected back, resulting in a loss of power and efficiency. The voltage standing wave ratio (VSWR) is a metric that indicates the amount of impedance mismatch in a transmission line. A higher VSWR means a higher impedance mismatch and a lower signal quality. A VSWR of 1:1 is ideal, meaning there is no impedance mismatch and no reflected power. A VSWR of 2:1 means that for every 2 units of forward power, there is 1 unit of reflected power12.
The other options are not correct because they do not affect the VSWR in RF cables. A high gain yagi antenna or a high gain parabolic dish antenna can increase the signal strength and directionality, but they do not cause impedance mismatch in the cable. Radio output power above 100 mW but below 400 mW is within the acceptable range for most WLAN devices and does not cause excessive VSWR in the cable3.
References: 1:CWNA-109Official Study Guide, page 77 2: VSWR 3:CWNA-109Official Study Guide, page
81
NEW QUESTION # 41
XYZ Company has decided to install an 802.11 WLAN system that will support 1083 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, and 802.11-2020 should be supported to provide the management frame protection and fast secure roaming security features?
- A. 802.11j and 802.11k
- B. 802.11k and 802.11v
- C. 802.11r and 802.11w
- D. 802.11j and 802.11z
Answer: C
Explanation:
The two IEEE amendments that should be supported to provide the management frame protection and fast secure roaming security features are 802.11r and 802.11w12.
* 802.11r (Fast BSS Transition): This amendment to the IEEE 802.11 standard permits continuous connectivity aboard wireless devices in motion, with fast and secure client transitions from one Basic Service Set to another1.
* 802.11w (Management Frame Protection): This amendment increases the security of its management frames2.
NEW QUESTION # 42
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. Wooden doors
- D. Elevators
Answer: D
Explanation:
Elevators are a common building item that frequently causes RF shadow and must be accounted for in coverage plans. RF shadow is a term that describes an area where wireless signals are blocked or significantly weakened by an obstacle or an object that absorbs or reflects RF energy.
RF shadow can cause lack of coverage or poor performance in a WLAN because wireless devices in those areas may not be able to communicate with access points or other devices. RF shadow can be mitigated by adjusting access point placement, antenna orientation, transmit power level, or channel selection to avoid or overcome the obstacle or object that causes it.
Elevators are a common building item that frequently causes RF shadow because they are made of metal and they move up and down within a shaft. Metal is a material that has high attenuation and reflection values, which means it can block or bounce off wireless signals very effectively. A moving elevator can create dynamic RF shadow that changes depending on its position and direction. Therefore, elevators must be accounted for in coverage plans to ensure adequate WLAN coverage and performance throughout the facility. The other options are not common building items that frequently cause RF shadow or must be accounted for in coverage plans.
Wooden doors are not likely to cause RF shadow because they are made of wood, which is a material that has low attenuation and reflection values, which means it can pass through or slightly weaken wireless signals. Carpeted floors are not likely to cause RF shadow because they are made of fabric, which is a material that has low attenuation and reflection values, which means it can pass through or slightly weaken wireless signals. Cubicle partitions are not likely to cause RF shadow because they are made of thin plastic or cardboard, which are materials that have low attenuation and reflection values, which means they can pass through or slightly weaken wireless signals.
NEW QUESTION # 43
You are performing a post-implementation validation survey. What basic tool can be used to easily locate areas of high co-channel interference?
- A. Throughput tester
- B. Laptop-based spectrum analyzer
- C. Wi-Fi scanner
- D. Access point spectrum analyzer
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.
NEW QUESTION # 44
When an ACK frame is not received by the transmitting STA, what is assumed?
- A. The receiver is offline
- B. The receiver processed the frame, but did not respond with an ACK frame because 802.11w is enabled
- C. The frame was not delivered and must be retransmitted
- D. The frame was correctly delivered
Answer: C
Explanation:
An ACK (Acknowledgement) frame is a short control frame that is sent by the receiver of a data or management frame to confirm that the frame was received correctly. The ACK frame is sent after a SIFS (Short Interframe Space) interval, which is the shortest time gap between frames in 802.11. If the transmitter does not receive an ACK frame within a specified time, it assumes that the frame was not delivered and must be retransmitted. This is part of the 802.11 reliability mechanism that ensures reliable data delivery over an unreliable wireless medium . References: [CWNA-109 Study Guide], Chapter 5: IEEE 802.11 Medium Access, page 209; [CWNA-109Study Guide], Chapter 5: IEEE 802.11 Medium Access, page 203.
NEW QUESTION # 45
You are implementing a VHT-capable AP. Which one of the following channels is available in the
802.11-2016 standard that was not available before the ratification of 802.11 ac?
- A. 0
- B. 1
- C. 2
- D. 3
Answer: C
Explanation:
Channel 144 is a new channel that was added to the 5 GHz band by the 802.11ac amendment, which defines the VHT (Very High Throughput) PHY for WLANs. Channel 144 has a center frequency of 5720 MHz and a bandwidth of 20 MHz. It can also be combined with adjacent channels to form wider channels of 40 MHz, 80 MHz, or 160 MHz. Channel 144 is available in some regions, such as North America and Europe, but not in others, such as Japan and China.
NEW QUESTION # 46
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