無料で使えるCWNA-108サンプル問題で100%カバー率のリアル試験問題（更新された123問あります)
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質問 # 47
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 other WLANs
- B. DoS attack
- C. Faulty drivers Dos attack
- D. Interference from no-Wi-Fi sources
正解：D
質問 # 48
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. 26 dBm
- B. 13 dBm
- C. 10 dBm
- D. 23 dBm
正解：D
解説：
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-108 Study Guide, Chapter 2: Radio Frequency Fundamentals, page 88.
質問 # 49
What 802.11 PHY uses available space in very low frequency ranges that is not in use at the time by broadcast video signals?
- A. SIG
- B. TVHT
- C. DMG
- D. DSSS
正解：B
解説：
Explanation
TVHT stands for Television Very High Throughput and it is a PHY defined by the 802.11af amendment. It uses the TV white space (TVWS) spectrum in the VHF and UHF bands between 54 and 790 MHz, which are not in use by broadcast video signals at the time. It can provide long-range and low-power connectivity for WLAN devices.
質問 # 50
What factor will have the most significant impact on the amount of wireless throughput available to each station within a BSS?
- A. The power management settings in the access point beacons
- B. The number of client stations associated to the BSS
- C. The presence of co-located (10m away) access points on non-overlapping channels
- D. The Layer 3 protocol used by each station to transmit data over the wireless link
正解：B
質問 # 51
What standard is referenced into the 802.11-2012 specification and is recommend for robust WLAN client security?
- A. WEP
- B. IPSec VPN
- C. SSID hiding
- D. 802.1X/EAP
正解：D
質問 # 52
What statement about the beamwidth of an RF antenna is true?
- A. Horizontal and vertical beamwidth are calculated at the points where the main lobe decreases power by
3 dB. - B. Vertical beamwidth is displayed (in degrees) on the antenna's Azimuth chart.
- C. When antenna gain is lower, the beamwidth is also lower in both the horizontal and vertical dimensions.
- D. The beamwidth patterns on an antenna polar chart indicate the point at which the RF signal stops propagating.
正解：A
解説：
Explanation
The beamwidth of an RF antenna is the angular measure of how wide the main lobe of radiation is. The main lobe is the area where the signal strength is highest and most concentrated. The beamwidth is calculated at the points where the main lobe decreases power by 3 dB, which means it is half of the maximum power. The beamwidth can be measured in both horizontal and vertical planes, depending on how the antenna is oriented.
The horizontal beamwidth is also called azimuth, while the vertical beamwidth is also called elevation. The beamwidth patterns on an antenna polar chart indicate how the RF energy is distributed in different directions. References: 1, Chapter 2, page 66; 2, Section 2.3
質問 # 53
What factors does not influence the distance at which an RF signal can be effectively received?
- A. Receiving station's output power
- B. Transmitting station's output power
- C. Receiving station's radio sensitivity
- D. Free Space Path Loss
正解：A
質問 # 54
An IEEE 802.11 amendment is in the draft state. What impact does this draft amendment have on the 802.11 standard?
- A. No impact: Until an amendment is ratified, it does not become part of the standard.
- B. No impact: Draft amendments do not become part of the standard until a working group is formed.
- C. Devices will be released based on the draft amendment and the draft amendment features are part of the standard.
- D. The standard is changed to reflect the new capabilities as soon as amendment enters the draft stage.
正解：A
質問 # 55
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. Bluetooth devices in the user's work area
- C. Excess RF energy from a nearby AP
- D. USB 3 devices in the user's work area
正解：A
質問 # 56
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. Passive
- C. Active
- D. Backup
正解：A
質問 # 57
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. FT
- B. Band steering
- C. Load balancing
- D. OKC
正解：A
質問 # 58
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
正解：B
解説：
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. References: 1, Chapter 8, page 309; 2, Section 5.2
質問 # 59
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. 802.11k and 802.11v
- B. 802.11j and 802.11k
- C. 802.11j and 802.11z
- D. 802.11r and 802.11w
正解：D
解説：
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.
質問 # 60
An 802.11-based network uses an AP and has several connecting clients. The clients include iPhones, iPads, laptops and one desktop. What WLAN use case is represented?
- A. Ad-hoc
- B. WPAN
- C. IBSS
- D. BSS
正解：D
解説：
Explanation
A BSS (Basic Service Set) is a WLAN use case that represents an 802.11-based network that uses an AP (Access Point) and has several connecting clients. The AP acts as a central point of coordination and communication for the clients, which can include iPhones, iPads, laptops, desktops, or any other devices that have Wi-Fi capabilities. A BSS can be identified by a unique BSSID (Basic Service Set Identifier), which is usually the MAC address of the AP's radio interface. A BSS can also be associated with an SSID (Service Set Identifier), which is a human-readable name that identifies the network. References: , Chapter 1, page 23; , Section 1.1
質問 # 61
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
正解：A
解説：
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 . References: [CWNA-109 Study Guide], Chapter 3: Antennas and Accessories, page 121; [CWNA-108 Study Guide], Chapter 3: Antennas and Accessories, page 115;
[Wikipedia], List of WLAN channels.
質問 # 62
An 802.11-based network uses an AP and has several connecting clients. The clients include iPhones, iPads, laptops and one desktop. What WLAN use case is represented?
- A. Ad-hoc
- B. WPAN
- C. IBSS
- D. BSS
正解：D
質問 # 63
The IEEE 802.11-2016 standard requires VHT capable devices to be backward compatible with devices using which other 802.11 physical layer specification (PHY)?
- A. OFDM
- B. DSSS
- C. ERP-PBCC
- D. HR/DSSS
正解：A
質問 # 64
In a WALN security, what authentication method always creates Layer2 dynamic encryption keys?
- A. EAP-TLS
- B. Shared Key
- C. HTTPS captive portal
- D. WEP
正解：D
質問 # 65
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 client drivers are faulty and should be upgraded.
- B. The access points are configured to disallow 5 GHz.
- C. The clients are configured to use WPA and 5 GHz channels only support WPA2.
- D. The antennas in the laptop have insufficient gain to detect the 5 GHz signals.
正解：A
解説：
Explanation
The client drivers are faulty and should be upgraded is the likely problem for the laptop that can see and connect to 2.4 GHz APs, but does not even see 5 GHz APs. The client drivers are the software components that enable the wireless adapter of the laptop to communicate with the operating system and the network. The client drivers are responsible for scanning the available wireless channels, detecting and connecting to the access points, negotiating the security and data rate parameters, and transmitting and receiving data frames. If the client drivers are faulty, outdated, or incompatible, they may cause various issues with the wireless performance and functionality, such as low data rates, poor signal strength, frequent disconnections, or inability to see or connect to certain access points or channels.
One of the possible causes of faulty client drivers is that they do not support or recognize some of the features or standards of the 802.11ac technology, such as wider channel bandwidths, higher modulation schemes, or DFS (Dynamic Frequency Selection) channels. This could explain why the laptop can see and connect to 2.4 GHz APs, but not 5 GHz APs, as 802.11ac operates only in the 5 GHz band and uses channels that are wider (up to 160 MHz) and higher (up to channel 165) than those used by previous standards. Moreover, some of the
5 GHz channels are subject to DFS rules, which require the access points and client stations to monitor and avoid using channels that are occupied by radar systems or other primary users. If the client drivers do not support or comply with DFS rules, they may not be able to see or connect to access points that use DFS channels.
To solve this problem, the client drivers should be upgraded to the latest version that supports and is compatible with 802.11ac features and standards. This can be done by downloading and installing the updated driver software from the manufacturer's website or using a device manager tool. Upgrading the client drivers may also improve other aspects of wireless performance and functionality, such as data rates, signal strength, security, and stability. References: 1, Chapter 12, page 493; 2, Section 8.1
質問 # 66
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