[2024年07月10日] 最新でリアルなCWNA-108試験問題集解答
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質問 # 35
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. IBSS
- C. BSS
- D. WPAN
正解：C
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 # 36
A client STA must choose the best AP for connectivity. As part of the evaluation, it must verify compatible data rates. What can the client STA use to verify that an AP supports the same data rates that it supports?
- A. Data frames sent between the AP and current clients STAs
- B. Authentication frames transmitted by the other client STAs
- C. Probe request frames transmitted by other client STAs
- D. Beacon frames transmitted by the AP
正解：D
解説：
Explanation
The client STA can use Beacon frames transmitted by the AP to verify that an AP supports the same data rates that it supports. Beacon frames are management frames that are periodically broadcasted by the APs to announce their presence, capabilities, and parameters. One of the information elements contained in the Beacon frames is the Supported Rates or Extended Supported Rates, which lists the data rates that the AP can use for communication. The client STA can compare its own data rates with those advertised by the AP to determine if they are compatible. Data frames, authentication frames, and probe request frames do not contain information about data rates. References: [CWNP Certified Wireless Network Administrator Official Study Guide: Exam CWNA-107], page 133; [CWNA: Certified Wireless Network Administrator Official Study Guide: Exam CWNA-106], page 123.
質問 # 37
What can cause excessive VSWR in RF cables used to connect a radio to an antenna?
- A. High gain parabolic dish antenna
- B. Impedance mismatch
- C. Radio output power above 100 mW but below 400 mw
- D. High gain yagi antenna
正解：B
解説：
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-108 Official Study Guide, page 77 2: VSWR 3: CWNA-108 Official Study Guide, page 81
質問 # 38
What cipher suite is specified by the 802.11-2016 standard and is not deprecated?
- A. Counter Mode with CBC-MAC Protocol
- B. Extensible Authentication Protocol
- C. Wired Equivalent Privacy
- D. Temporal Key Integrity Protocol
正解：A
解説：
Explanation
The cipher suite specified by the 802.11-2016 standard and is not deprecated is Counter Mode with CBC-MAC Protocol (CCMP). CCMP is an encryption protocol that uses Advanced Encryption Standard (AES) as the underlying cipher and provides confidentiality, integrity, and origin authentication for wireless data. CCMP is the mandatory encryption protocol for WPA2 and WPA3. References: [CWNP Certified Wireless Network Administrator Official Study Guide: Exam CWNA-107], page 295; [IEEE Standard for Information technology-Telecommunications and information exchange between systems Local and metropolitan area networks-Specific requirements - Part 11: Wireless LAN Medium Access Control (MAC) and Physical Layer (PHY) Specifications], page 1560.
質問 # 39
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. RTS
- B. ACK
- C. Beacon
- D. PS-Poll
正解：A
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 # 40
What security method is commonly used for VoIP handsets when the infrastructure does not support OKC or FT roaming?
- A. WPA2-Enterprise with PEAP
- B. WPA2-Enterprise with EAP-TLS
- C. WPA2 -Personal
- D. WPA2-Enterprise with EAP-TTLS
正解：B
質問 # 41
What statement is true concerning the use of Orthogonal Frequency Division Multiplexing (OFDM) modulation method in IEEE 802.11 WLANs?
- A. OFDM was used by Frequency Hopping Spread Spectrum (FHSS) PHY devices.
- B. OFDM modulation is used only in 5 GHz 802.11 transmissions.
- C. OFDM was first introduced in 802.11a and is used by the ERP, HT and VHT PHYs as well.
- D. OFDM implements BPSK modulation to allow for data rates up to 7 Gbps.
正解：C
解説：
https://en.wikipedia.org/wiki/IEEE_802.11
質問 # 42
ABC Company is planning a point-to-multipoint outdoor bridge deployment with standalone (autonomous) 802.11 bridge units. 802.1X/EAP will be used for bridge authentication. A Linux- based RADIUS server will be used for authentication. What device in the bridge Implementation as the 802.1X Authenticator?
- A. All non-root bridges
- B. The root bridge
- C. The RADIUS server
- D. The Ethernet switch
正解：D
質問 # 43
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 802.11acAP. Both the client and AP are 2x2:2 devices.
What is the likely cause of the low data rate issue?
- A. Too few spatial streams
- B. CAT5e cabling run to the AP
- C. Lack of support for 802.11n
- D. Weak signal strength
正解：D
質問 # 44
XYZ Corporation is experiencing connectivity problems with their existing building-to-building bridge link. A concrete wall on the roof of one building is partially blocking the Fresnel Zone, and the connection is dropping many frames. The administrator moves the antenna to an area not obstructed by the concrete wall and then realizes the RF cable cannot reach the new location.
If an extension cable is added to move the antenna, what are the likely results?
- A. The likelihood of a direct lightning strike will increase.
- B. The data throughput rate will increase because VSWR will decrease.
- C. The Equivalent Isotropically Radiated Power (EIRP) will decrease.
- D. The antenna's azimuth beamwidth will decrease.
- E. The size of the Fresnel zone will increase.
正解：C
質問 # 45
What statement about 802.11 WLAN bridges is true?
- A. WLAN bridges must use a channel with acceptable SNR at both transceivers to maintain the desired data rate bi-directionally
- B. WLAN bridges may support MIMO communication, but only if used in the GHz frequency band
- C. WLAN bridges only work in the 2.4 GHz frequency band and they support only SISO communications
- D. WLAN bridges must be implemented such that no interference occurs on the channel anywhere between the two endpoints used to establish the bridge
正解：B
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 # 46
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. Overlay WLAN monitoring solution
- D. laptop-based protocol analyzers
正解：B
質問 # 47
When compared with legacy Power Save mode, how does VHT TXOP power save improve battery life for devices on a WLAN?
- A. VHT TXOP power save allows stations to enter sleep mode and legacy Power Save does not.
- B. VHT TXOP power save allows the WLAN transceiver to disable more components when in a low power state.
- C. VHT TXOP power save uses the partial AID in the preamble to allow clients to identify frames targeted for them.
- D. Legacy Power Save mode was removed in the 802.11ac amendment.
正解：C
解説：
Explanation
VHT TXOP power save uses the partial AID in the preamble to allow clients to identify frames targeted for them. VHT TXOP power save is a feature introduced in the 802.11ac amendment that improves battery life for devices on a WLAN by allowing them to enter sleep mode more frequently and for longer periods of time. It works by using a new field called partial AID in the preamble of VHT frames that indicates which stations are addressed by the frame. This allows stations to quickly determine if they need to wake up and receive the frame or stay in sleep mode and save power. This reduces the overhead and latency of legacy Power Save mode, which requires stations to wake up periodically and listen to Beacon frames or other control frames to check if there are any buffered frames for them at the AP. References: , Chapter 3, page 117; , Section 3.2
質問 # 48
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. Overlay WLAN monitoring solution
- B. Laptop-based protocol analyzers
- C. AP-based spectrum analysis
- D. Laptop-based spectrum analyzers
正解：A
質問 # 49
What information is transmitted in the Beacon management frames of an HT access point to communicate about backward compatibility with ERP and HR/DSSS stations? (Choose 2)
- A. HT Protection mode
- B. Power save mode of clients
- C. Secondary channel offset
- D. RIFS mode
- E. Non-ERP Present field
正解：A、C
質問 # 50
The IEEE 802.11-2012 standard requires VHT capable devices to be backward compatible with devices using which other 802.11 physical layer specification (PHY)?
- A. ERP-PBCC
- B. OFDM
- C. DSSS
- D. HR/DSSS
正解：B
質問 # 51
You are performing a post implementation validation survey. What basic tool can be used to easily locate areas of high co-channel interference?
- A. Wi-Fi scanner
- B. Access point spectrum analyzer
- C. Throughput tester
- D. Laptop-based spectrum analyzer
正解：B
質問 # 52
What factors are likely to cause the greatest impact on the application layer throughput of an
802.11n client station in a 2.4 GHz HT BSS? (Choose 3)
- A. Increasing or decreasing the number of spatial streams in use by the client station and AP
- B. Use of passphrase authentication instead of 802.1X/EAP authentication
- C. Use of WEP or TKIP for encryption instead of CCMP
- D. RF interference from more than 10 nearby Bluetooth transmitters
- E. Increasing the beacon interval from 100 to 200 (TUs)
正解：A、C、D
質問 # 53
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CWNA-108認証試験問題集の解答を提供しています：https://drive.google.com/open?id=1j0Te82wE57W4iQtPZkT3i2b02HSCJvxF
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