無料CWNA-108試験ブレーン問題集認定ガイド問題と解答
CWNA-108認定概要最新のCWNA-108PDF問題集
質問 # 53
What best describes WPA2 in relation to 802.11 wireless networks?
- A. WPA2 is specified in the 802.11 standard as implementing CCMP/AES.
- B. WPA2 is a certification created by the Wi-Fi Alliance that validates devices correctly implement CCMP/ AES.
- C. WPA2 is the standard that defines security for WLANs.
- D. WPA2 is the second version of WPA and it enhances security through the use of TKIP instead of WEP.
正解：C
質問 # 54
You are implementing a VHT-capable AP. Which one of the following channels is available in the
802.11ac amendment to the 802.11-2012 standard, which was not available in the standard before this amendment?
- A. 0
- B. 1
- C. 2
- D. 3
- E. 4
正解：B
質問 # 55
Which directional antenna types are commonly used by indoor Wi-Fi devices in a MIMO multiple spatial stream implementation?
- A. Dish and grid
- B. Grid and sector
- C. Dipole and yagi
- D. Patch and panel
正解：C
質問 # 56
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. USB 3 devices in the user's work area
- C. Bluetooth devices in the user's work area
- D. Excess RF energy from a nearby AP
正解：B
解説：
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,
質問 # 57
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 for voice over Wi-Fi. what is an action that must be performed?
- A. Application analysis with an active phone call on a VoWiFi handset
- B. Spectrum analysis to locate and identity RF Interference sources
- C. Protocol analysis to discover channel use on neighboring APs
- D. Frequency-band hopping analysis to detect improper RF channel implementations
正解：B
質問 # 58
When an ACK frame is not received by the transmitting STA, what is assumed?
- A. The frame was correctly delivered
- B. The frame was not delivered and must be retransmitted
- C. The receiver processed the frame, but did not respond with an ACK frame because Q3
11w is enabled - D. The receiver is offline
正解：B
質問 # 59
What statement about 802.3, Clause 33 Power over Ethernet is true?
- A. Only endpoint PSEs are supported.
- B. Only midspan PSEs are supported.
- C. When using CAT5 cabling, you increase the maximum draw available to the PD over that available with CAT6.
- D. The lowest voltage drop is achieved when using CAT6 cable instead of Cat5 or CAT5e.
正解：D
解説：
https://www.cablinginstall.com/articles/2012/08/cat-6a-vs-cat-5e-poe.html
質問 # 60
Your manager asked you to locate a solution that allows for centralized monitoring of WLAN performance over time. He wants a single pane of glass for administration and monitoring of the solution. What do you recommend?
- A. Laptop-based spectrum analyzers
- B. AP-based spectrum analysis
- C. Laptop-based protocol analyzers
- D. Overlay WLAN monitoring solution
正解：D
質問 # 61
What factor is likely to cause the least impact on the application layer throughput of an 802.11n client station in a 2.4 GHz HT BSS?
- A. RF interference from more than 10 nearby Bluetooth transmitters
- B. Implementation Fast BSS Transition (FT) for roaming
- C. Increasing or decreasing the number of spatial streams in use by the client station and AP
- D. Implementation of several other clients in the same BSS using 802.11g radios.
正解：B
解説：
https://www.networkcomputing.com/wireless-infrastructure/wifi-fast-roaming-simplified
質問 # 62
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. Residential
- B. Standard office
- C. High density
- D. SOHO
正解：C
解説：
Explanation
A high-density deployment is a wireless network that is designed to support a large number of users and devices in a relatively small area. This type of deployment is often used in enterprise environments, such as offices, schools, and hospitals.
The use of semi-directional antennas in the deployment described in the question is a good indication that it is a high-density deployment. Semi-directional antennas can be used to focus the signal from an access point in a specific direction. This can help to reduce interference and improve performance in high-density environments.
The other answer choices are less likely to be correct for the following reasons:
* SOHO (small office/home office) deployments are typically smaller and less complex than high-density deployments.
* Residential deployments are typically even smaller and less complex than SOHO deployments.
* Standard office deployments may be high-density, but they may also be lower-density.
It is important to note that the type of deployment is not determined solely by the output power of the access points. However, the use of 10 mW of output power on the 2.4 GHz radios and 20 mW of output power on the
5GHz radios is also consistent with a high-density deployment.
Here are some additional tips for deploying a high-density wireless network:
* Use a site survey to determine the optimal placement of access points.
* Configure the access points to use non-overlapping channels.
* Use semi-directional or directional antennas to focus the signal and reduce interference.
* Implement a wireless intrusion prevention system (WIPS) to detect and mitigate rogue access points and other security threats.
質問 # 63
You are implementing a multi-AP WLAN and fast secure roaming is essential.
Which one of the following methods is an IEEE 802.11 standard method for fast roaming?
- A. Band Steering
- B. Load balancing
- C. FT
- D. OKC
正解：C
解説：
https://www.cisco.com/c/en/us/td/docs/wireless/controller/8-1/Enterprise-Mobility-8-1- DesignGuide/Enterprise_Mobility_8-1_Deployment_Guide/Chapter-11.pdf
質問 # 64
Return Loss is the decrease of forward energy in a system when some of the power is being reflected back toward the transmitter. What will cause high return loss in an RF transmission system, including the radio, cables, connectors and antenna?
- A. A significant impedance mismatch between components in the RF system
- B. The use of 50 ohm cables longer than one meter in the RF system
- C. A Voltage Standing Wave Ratio (VSWR) of 1:1
- D. High output power at the transmitter and use of a low-gain antenna
正解：A
解説：
Explanation
Return loss is a measure of how well the components of an RF system are matched in terms of their impedance. Impedance is the opposition to the flow of alternating current in a circuit, and it depends on the frequency, resistance, capacitance, and inductance of the components. When the impedance of the source, the transmission line, and the load are not equal, some of the power is reflected back to the source, causing a loss of forward power. This loss is expressed in decibels (dB) as return loss. The higher the return loss, the lower the reflection and the better the impedance matching. Conversely, the lower the return loss, the higher the reflection and the worse the impedance matching.
VSWR (Voltage Standing Wave Ratio) is another way of expressing the same concept. It is the ratio of the maximum voltage to the minimum voltage along a transmission line due to the interference of the incident and reflected waves. A VSWR of 1:1 means that there is no reflection and perfect impedance matching. A VSWR higher than 1:1 means that there is some reflection and impedance mismatch. The higher the VSWR, the higher the reflection and the lower the return loss.
Therefore, a significant impedance mismatch between components in an RF system will cause high reflection, high VSWR, and low return loss.
質問 # 65
What answer correctly completes the following sentence?
____________ and physical carrier sense functions are used to determine if the wireless medium is busy.
- A. Virtual
- B. Active
- C. Backup
- D. Passive
正解：A
質問 # 66
What best describes WPA2 in relation to 802.11 wireless network?
- A. WPA2 is a certification created by the Wi-Fi Alliance that validates device correctly implement CCMP/AES.
- B. WPA2 is specified in the 802. 11 standard as implementing CCMP/AES
- C. WPA2 is the second version of WPA and it enhances security through the use of TKIP Instead of WEP.
- D. WPA2 is the standard that defines security for WLANs.
正解：D
質問 # 67
Your manager asked you to locate a solution that allows for centralized monitoring of WLAN performance over time. He wants a single pane of glass for administration and monitoring of the solution. What do you recommend?
- A. Laptop-based spectrum analyzers
- B. AP-based spectrum analysis
- C. Laptop-based protocol analyzers
- D. Overlay WLAN monitoring solution
正解：D
解説：
Explanation
The solution that you recommend is an Overlay WLAN monitoring solution. An Overlay WLAN monitoring solution is a system that uses dedicated sensors or probes to monitor the WLAN performance over time. The sensors are deployed throughout the WLAN coverage area and collect data on various metrics such as signal strength, noise level, channel utilization, interference, throughput, latency, packet loss, and QoS. The sensors send the data to a centralized server or appliance that analyzes the data and provides a single pane of glass for administration and monitoring of the solution. An Overlay WLAN monitoring solution can help to detect and troubleshoot WLAN issues, optimize WLAN performance, and generate reports and alerts. References: [CWNP Certified Wireless Network Administrator Official Study Guide: Exam CWNA-107], page 538; [CWNA: Certified Wireless Network Administrator Official Study Guide: Exam CWNA-106], page 508.
質問 # 68
You are troubleshooting a problem with interference from a non-802.11 device. Given that the device is not a WLAN device, you cannot use a protocol analyzer and have chosen to use a spectrum analyzer. You want to view the signal from the interfering device over time to sec the activity that it is generating. What common spectrum analyzer view should you use for this analysis?
- A. APs
- B. Real-Time FFT
- C. Waterfall/Spectrogram
- D. Clients
正解：C
質問 # 69
What statement about 802.11 WLAN bridges is true?
- A. WLAN bridges must be implemented such that no interference occurs on the channel anywhere between the two endpoints used to establish the bridge
- B. WLAN bridges must use a channel with acceptable SNR at both transceivers to maintain the desired data rate bi-directionally
- C. WLAN bridges may support MIMO communication, but only if used in the GHz frequency band
- D. WLAN bridges only work in the 2.4 GHz frequency band and they support only SISO communications
正解：C
解説：
https://www.apm.com.tw/mimo-300mbps-outdoor-bridge-2-4ghz-ape-2405mm8.html WiGig Is 802.11ad and 802.11ay WiGig transmits data wirelessly on the 60 GHz frequency published in 2012, uses the 802.11ad standard offer 5Gbps at up to 10 meters release in 2019, 802.11ay is scheduled for release in
2019 offering 10Gbps at up to 100 meters
Wifi 6
802.11ax,
https://www.cnet.com/home/internet/wi-fi-6-and-what-it-means-for-you-wifi-routers/ WPA3 WPA3 standard also replaces the pre-shared key (PSK) exchange with Simultaneous Authentication of Equals (SAE) WPA3 The new standard uses an equivalent 192-bit cryptographic strength in WPA3-Enterprise mode Protection of management frames as specified in the IEEE 802.11w amendment is also enforced by the WPA3 specifications.
質問 # 70
When compared with legacy Power Save mode, how does VHT TXOP power save improve battery life for devices on a WLAN?
- A. Legacy Power Save mode was removed in the 802.11ac amendment.
- B. VHT TXOP power save allows stations to enter sleep mode and legacy Power Save does not.
- C. VHT TXOP power save uses the partial AID in the preamble to allow clients to identify frames targeted for them.
- D. VHT TXOP power save allows the WLAN transceiver to disable more components when in a low powerstate.
正解：A
質問 # 71
What frame type is used to reserve the wireless medium for the transmission of high data rate frames that may not be understood by all clients connected to the BSS?
- A. PS-Poll
- B. ACK
- C. Beacon
- D. RTS
正解：D
解説：
Explanation
The frame type that is used to reserve the wireless medium for the transmission of high data rate frames that may not be understood by all clients connected to the BSS is RTS. RTS stands for Request to Send and is a control frame that is sent by a station to request access to the medium for a specified duration. The RTS frame contains the source and destination MAC addresses, as well as a Network Allocation Vector (NAV) value that indicates how long the medium will be occupied. The destination station responds with a Clear to Send (CTS) frame that echoes the NAV value and grants permission to the source station. All other stations in the BSS hear either the RTS or CTS frame and update their NAV timers accordingly, deferring their transmissions until the medium is free. The RTS/CTS mechanism can be used to prevent hidden node problems, reduce collisions, and protect high data rate frames that use features such as 802.11n or 802.11ac that may not be compatible with legacy stations. ACK, Beacon, and PS-Poll are not used to reserve the medium for high data rate frames. References: [CWNP Certified Wireless Network Administrator Official Study Guide: Exam CWNA-107], page 112; [CWNA: Certified Wireless Network Administrator Official Study Guide: Exam CWNA-106], page 102.
質問 # 72
What standard is referenced into the 802.11-2012 specification and is recommend for robust WLAN client security?
- A. IPSec VPN
- B. 802.1X/EAP
- C. WEP
- D. SSID hiding
正解：B
質問 # 73
What is the final step in an effective troubleshooting process?
- A. Document the results
- B. Notify the users of problem resolution
- C. Verify the solution
- D. Disable the WLAN
正解：A
解説：
Explanation
The final step in an effective troubleshooting process is to document the results. Documentation is essential for keeping track of the problem history, the actions taken, the solutions implemented, and the outcomes achieved.
Documentation can also help to prevent future problems, improve best practices, and provide feedback for improvement. Documentation should include relevant information such as problem description, symptoms, root cause analysis, resolution steps, verification methods, and lessons learned. References: [CWNP Certified Wireless Network Administrator Official Study Guide: Exam CWNA-107], page 513; [CWNA: Certified Wireless Network Administrator Official Study Guide: Exam CWNA-106], page 483.
質問 # 74
What statement about 802.11 WLAN performance is true?
- A. In most WLANs, no special skill or tuning is required to get peak performance
- B. To get the best performance out of an AP, you should disable data rates of 72 Mbps and lower
- C. In modem networks, both centralized and distributed data forwarding work well for most standard office deployments
- D. WLANs perform better as more wireless clients connect with each AP
正解：C
解説：
Explanation
The statement that in modern networks, both centralized and distributed data forwarding work well for most standard office deployments is true about WLAN performance. Data forwarding refers to how wireless frames are transmitted from wireless clients to wired networks or vice versa through wireless access points (APs).
Centralized data forwarding means that all wireless frames are sent to a central controller or gateway before being forwarded to their destinations. Distributed data forwarding means that wireless frames are forwarded directly by the APs to their destinations without going through a central controller or gateway. Both methods have their advantages and disadvantages, depending on the network size, topology, traffic pattern, security, and management requirements. However, in modern networks, both methods can achieve high performance and scalability for most standard office deployments, as they can leverage advanced features such as fast roaming, load balancing, quality of service, and encryption. The other statements about WLAN performance are false. In most WLANs, special skill or tuning is required to get peak performance, such as selecting the appropriate channel, power, data rate, and antenna settings. WLANs perform worse as more wireless clients connect with each AP, as they cause more contention and interference on the wireless medium. To get the best performance out of an AP, you should not disable data rates of 72 Mbps and lower, as they are needed for backward compatibility and range extension. References: CWNA-109 Study Guide, Chapter 9: Wireless LAN Architecture, page 2811
質問 # 75
When antenna gain is reported in dBi, the gain of the antenna is compared to what theoretical radiator?
- A. Dipole radiator
- B. Anthropomorphic radiator
- C. Isotropic radiator
- D. End-fire radiator
正解：C
解説：
Explanation
An isotropic radiator is a theoretical point source of electromagnetic radiation that radiates equally in all directions. It has no physical dimensions and no preferred direction of radiation. It is used as a reference for antenna gain because it represents the ideal case of a perfect omnidirectional antenna12 Antenna gain is a measure of how well an antenna concentrates its radiated power in a certain direction. It is expressed in decibels (dB) relative to a reference antenna. When the reference antenna is an isotropic radiator, the antenna gain is denoted by dBi, which stands for decibels relative to isotropic12 For example, an antenna with a gain of 3 dBi means that it radiates 3 dB more power in its main direction than an isotropic radiator would. Conversely, an antenna with a gain of -3 dBi means that it radiates 3 dB less power in its main direction than an isotropic radiator would12
質問 # 76
What is always required to establish a high quality 2.4 GHz RF link at a distance of 3 miles (5 kilometers)?
- A. Grid antennas ateach endpoint
- B. A Fresnel Zone that is at least 60% clear of obstructions
- C. Minimum output power level of 2 W
- D. A minimum antenna gain of 11 dBi at both endpoints
正解：B
解説：
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-107], page 75; [CWNA: Certified Wireless Network Administrator Official Study Guide: Exam CWNA-106], page 65.
質問 # 77
What factors will have the most significant impact on the amount of wireless bandwidth available to each station within a BSS? (Choose 2)
- A. The number of clientstations associated to the BSS
- B. The presence of co-located (10m away) access points on non-overlapping channels
- C. The layer 3 protocol used by each station to transmit data over the wireless link
- D. The power management settings in the access point's beacons
正解：A
解説：
Explanation
The factors that will have the most significant impact on the amount of wireless bandwidth available to each station within a BSS are:
* The number of client stations associated to the BSS
* The presence of co-located (10m away) access points on non-overlapping channels The number of client stations associated to the BSS affects the wireless bandwidth because each station shares the same channel and medium with other stations in the same BSS. The more stations there are, the more contention and collision there will be for the channel access, which reduces the throughput and efficiency of the wireless communication. The wireless bandwidth available to each station depends on how the access point allocates the channel resources and how the stations use the channel time. For example, if the access point uses a round-robin scheduling algorithm, each station will get an equal share of the channel time regardless of its data rate or traffic demand. However, if the access point uses a proportional fair scheduling algorithm, each station will get a share of the channel time that is proportional to its data rate and traffic demand, which may result in higher or lower bandwidth for different stations.
The presence of co-located (10m away) access points on non-overlapping channels affects the wireless bandwidth because even though they use different channels, they may still cause interference and noise to each other due to channel leakage or imperfect filtering. The interference and noise can degrade the signal quality and SNR of the wireless communication, which reduces the data rate and throughput of the wireless communication. The wireless bandwidth available to each station depends on how well the access point and the station can cope with the interference and noise from other channels. For example, if the access point and the station support dynamic frequency selection (DFS) or adaptive radio management (ARM), they can switch to a less congested channel or adjust their output power or antenna gain to avoid or minimize interference from other channels.
References: 1, Chapter 3, page 94; 2, Section 3.2
質問 # 78
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