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CWNP CWAP-404 認定試験の出題範囲：
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質問 # 111
Finish the statement. It is possible to distinguish between _______and ______20 MHz transmissions when looking at an FFT plot.
- A. HR/DSSS and ERP
- B. ERP and VHT
- C. HT and VHT
- D. OFDM and HT
正解：D
解説：
It is possible to distinguish between OFDM 20 MHz transmissions and HT 20 MHz transmissions when looking at an FFT plot. OFDM and HT are two different modulation schemes used by
802.11 WLANs. OFDM is used by legacy 802.11a/g devices, while HT is used by newer
802.11n/ac devices. OFDM and HT have different spectral characteristics that can be observed on an FFT plot. OFDM transmissions have a flat spectrum with sharp edges, while HT transmissions have a tapered spectrum with rounded edges. This is because HT uses guard intervals and cyclic prefixes to reduce inter-symbol interference and improve performance. The other options are not correct, as they do not describe different modulation schemes or channel widths that can be distinguished on an FFT plot.
質問 # 112
A PHY Header is added to the PSDU at which layer?
- A. PHY
- B. LLC
- C. Network
- D. MAC
正解：A
解説：
Explanation
A PHY header is added to the PSDU at the PHY layer. A PHY header is a part of the PPDU that contains information such as modulation, coding, and data rate. The PHY header is added by the PHY layer when it converts a PSDU to a PPDU for transmission, or removed by the PHY layer when it converts a PPDU to a PSDU for reception. The other layers do not add or remove a PHY header. References: [Wireless Analysis Professional Study Guide CWAP-404], Chapter 4: 802.11 Physical Layer, page 97-98
質問 # 113
As a wireless network consultant you have been called in to troubleshoot a high-priority issue for one of your customers. The customer's office is based on two floors within a multi-tenant office block. On one of these floors (floor 5) users cannot connect to the wireless network. During their own testing the customer has discovered that users can connect on floor 6 but not when they move to the floor 5. This issue is affecting all users on floor 5 and having a negative effect on productivity.
To troubleshoot this issue, you perform both Spectrum and Protocol Analysis. The Spectrum Analysis shows the presence of Bluetooth signals which you have identified as coming from wireless mice. In the protocol analyzer you see the top frame on the network is Deauthentication frames. On closer investigation you see that the Deauthentication frames' source addresses match the BSSIDs of your customers APs and the destination address is FF:FF:FF:FF:FF:FF:FF.
What do you conclude from this troubleshooting exercise?
- A. The customers APs are misbehaving and a technical support case should be open with the vendor
- B. The users on floor 5 are being subjected to a denial of service attack, as this is happening across the entire floor it is likely to be a misconfigured WIPS solution belonging to the tenants on the floor below
- C. The customer should replace all their Bluetooth wireless mice as they are stopping the users on floor 5 from connecting to the wireless network
- D. The CCI from the APs on the floor 4 is the problem and you need to ask the tenant below to turn down their APs Tx power
正解：B
解説：
Explanation
The users on floor 5 are being subjected to a denial of service attack, as this is happening across the entire floor it is likely to be a misconfigured WIPS solution belonging to the tenants on the floor below. This is because the Deauthentication frames have a source address that matches the BSSIDs of the customer's APs and a destination address that is a broadcast address (FF:FF:FF:FF:FF:FF). This indicates that someone is sending spoofed Deauthentication frames to all STAs associated with the customer's APs, causing them to disconnect from the wireless network. This is a common type of DoS attack on wireless networks, and it could be caused by a rogue device or a WIPS solution that is configured to protect the wireless network of another tenant on the floor below12. References: CWAP-404 Certified Wireless Analysis Professional Study and Reference Guide, Chapter 13: Troubleshooting Common Wi-Fi Issues, page 4961; CWAP-404 Certified Wireless Analysis Professional Study and Reference Guide, Chapter 14: Troubleshooting Tools, page 5272.
質問 # 114
Which statement accurately describes IEEE 802.11 Power Save operation in a Basic Service Set that does not support the QoS facility?
- A. When the access point's buffer is full, the access point wakes all client stations using a PS-Poll frame so that they can receive the data.
- B. After waking from a low power state, client stations listen for the next Beacon to determine if sending a PS-Poll frame to the access point is necessary.
- C. Upon receiving traffic for a dozing station, the access point wakes the client station using a PS- Poll frame so that the client station can receive the data.
- D. After waking at a scheduled TBTT, client stations send Null Function frames to the access point with the Power Management bit set back to zero.
- E. Following a period of time in a low power state, client stations wake themselves and automatically poll the access point for traffic using a PS-Poll frame.
正解：B
質問 # 115
You require 802.11ac capture solution.
You want to capture using native operating system tools if possible.
What operating system has built-in ability to capture 802.11ac frames assuming it is running on the appropriate laptop hardware?
- A. Windows 8.1
- B. Mac OS X
- C. Windows 10
- D. Windows 7
正解：B
質問 # 116
To what data rates can a 5 GHz PHY device shift when changers occur in the signal strength?
- A. 24, 18, 12, 5.5
- B. 11, 5.5, 2, 1
- C. 24, 18, 11, 2
- D. 24, 18, 12, 6
正解：D
質問 # 117
Which one of the these is the most important in the WLAN troubleshooting methodology among those listed?
- A. Observe the problem
- B. Interview the network manager about the issues being experienced
- C. Talk to the end users about their experiences
- D. Obtain detailed knowledge of the wireless vendors debug and logging options
正解：A
解説：
Observing the problem is the most important step in the WLAN troubleshooting methodology among those listed. This step involves capturing and analyzing the relevant data from the wireless network, such as packets, frames, spectrum, and performance metrics. Observing the problem helps to verify the existence and scope of the issue, identify the root cause and possible solutions, and validate the results of any actions taken. The other steps are also important, but they are not as critical as observing the problem.
質問 # 118
You are troubleshooting problems with DHCP in relation to lightweight APs. They vendor class identifier (VCI) is not specified in the DHCP server. When you contact vendor support, they inform you that it is not necessary.
When is this information true?
- A. When only one client option 43 value is required
- B. When the DHCP server is directly connected to the subnet
- C. When only one AP exists on the subnet
- D. When only one client option 60 value is required
正解：A
質問 # 119
You have installed a new 802.11ac WLAN configured with 80 MHz channels. Users in one area are complaining about poor performance. This area is currently served by a single AP. You take a spectrum analysis capture in the poor performing area. While examining the waterfall plot you notice the airtime utilization is higher on the first 20 MHz of the 80 MHz channel when compared to the rest of the channel. What do you conclude?
- A. The AP is misconfigured and needs to be reconfigured to 80MHz operation
- B. RRM is enabled and has dynamically picked a 20 MHz channel
- C. The first 20 MHz is the AP's primary channel and higher airtime utilization on the primary channel is normal when an AP Is configured for 80 MHz operation
- D. Non Wi-Fi interference is preventing the APs 80 MHz operation
正解：D
解説：
The most likely cause of higher airtime utilization on the first 20 MHz of the 80 MHz channel is non- Wi-Fi interference. Non-Wi-Fi interference can prevent an AP from using its full channel width, as it will degrade the signal quality and increase the noise floor on some parts of the channel. This will force the AP to fall back to a narrower channel width, such as 20 MHz or 40 MHz, to maintain communication with its clients. The waterfall plot can help identify non-Wi-Fi interference by showing spikes or bursts of RF energy on specific frequencies or sub-channels.
The other options are not correct, as they do not explain why only the first 20 MHz of the channel has higher airtime utilization.
質問 # 120
A manufacturing facility has installed a new automation system which incorporates an 802.11 wireless network. The automation system is controlled from tablet computers connected via the WLAN. However, the automation system has not gone live due to problem with the tablets connecting to the WLAN. The WLAN vendor has been onsite to perform a survey and confirmed good primary and secondary coverage across the facility. As a CWAP you are called in to perform Spectrum Analysis to identify any interference sources.
From the spectrum analysis, you did not identify any interference sources but were able to correctly identify the issue. Which of the following issues did you identify from the spectrum analysis?
- A. A high noise floor has resulted in a SNR of less than 20dB
- B. The tablets are connecting to the wrong SSID
- C. There is a power mismatch between the APs and the clients
- D. The tablets are entering power save mode and failing to wake up to receive the access points transmissions
正解：C
解説：
Explanation
The most likely issue that can be identified from the spectrum analysis is a power mismatch between the APs and the clients. A power mismatch occurs when the APs transmit at a higher power level than the clients, or vice versa. This can cause asymmetric communication, where one side can hear the other, but not vice versa.
This can result in poor performance, disconnections, or packet loss. A spectrum analysis can reveal a power mismatch by showing different signal amplitudes or RSSI values for the APs and the clients on the same channel or frequency. The other options are not correct, as they cannot be identified from the spectrum analysis alone. The tablets' SSID, power save mode, and noise floor can be determined by using other tools or methods, such as protocol analysis, site survey, or device configuration. References: [Wireless Analysis Professional Study Guide CWAP-404], Chapter 3: Spectrum Analysis, page 79-80
質問 # 121
How is the length of an AIFS calculated?
- A. DIFS + SIFS + AIFSN
- B. SIFS + AIFS * Time Unit
- C. AIFSN * Slot Time + SIFS
- D. SIFS * Slot Time + AIFSN
正解：C
解説：
Explanation
The length of an AIFS (Arbitration Interframe Space) is calculated by multiplying the AIFSN (Arbitration Interframe Space Number) by the Slot Time and adding the SIFS (Short Interframe Space). An AIFS is a variable interframe space introduced by 802.11e to help prioritize medium access for different Access Categories (ACs). An AC is a logical queue that corresponds to a QoS (Quality of Service) level for different types of traffic. Each AC has a different AIFSN value, which determines how long it has to wait before attempting to access the medium. A lower AIFSN value means a higher priority and a shorter waiting time.
The Slot Time is a fixed value that depends on the PHY type and channel width. The SIFS is the shortest interframe space that is used for high-priority transmissions, such as ACKs or CTSs. The formula for calculating the AIFS length is: AIFS = AIFSN * Slot Time + SIFS. References: [Wireless Analysis Professional Study Guide CWAP-404], Chapter 7: QoS Analysis, page 194-195
質問 # 122
Which piece of information Is not transmitted in an HT PDDU header?
- A. MCS index
- B. PPDU length
- C. Number of Spatial Streams
- D. Channel number
正解：D
解説：
The channel number is not transmitted in an HT PPDU header. An HT PPDU header is a part of the PPDU that contains information such as modulation, coding, data rate, and number of spatial streams for an 802.11n transmission. The channel number is not included in the HT PPDU header, as it is determined by the frequency band and channel width that are used by the transmitter and receiver. The channel number can be inferred from the frequency band and channel width, which are indicated by bits in different fields of the HT PPDU header, such as HT- SIG and HT-LTF. The other options are not correct, as they are transmitted in an HT PPDU header. The number of spatial streams, PPDU length, and MCS index are indicated by bits in the HT-SIG field of the HT PPDU header.
質問 # 123
What is the function of the PHY layer?
- A. Convert PPDUs to PSDUs for transmissions and PSDUs to PPDUs for receptions
- B. Convert MSDUs to PPDUs for transmissions and PPDUs to MSDUs for receptions
- C. Convert PSDUs to PPDUs for transmissions and PPDUs to PSDUs for receptions
- D. Convert PPDUs to MSDUs for transmissions and MSDUs to PPDUs for receptions
正解：C
解説：
The function of the PHY layer is to convert PSDUs to PPDUs for transmissions and PPDUs to PSDUs for receptions. A PSDU (PHY Service Data Unit) is the data unit that is passed from the MAC layer to the PHY layer for transmission, or from the PHY layer to the MAC layer for reception. A PPDU (PHY Protocol Data Unit) is the data unit that is transmitted or received over the wireless medium by the PHY layer. A PPDU consists of a PSDU and a PHY header, which contains information such as modulation, coding, and data rate. The PHY layer adds or removes the PHY header to or from the PSDU during the conversion process.
質問 # 124
Which one of the following is not an 802.11 Management frame?
- A. Authentication
- B. Beacon
- C. PS-Poll
- D. Action
正解：C
解説：
A PS-Poll (Power Save Poll) frame is not an 802.11 management frame. A PS-Poll frame is a type of control frame that is used by a STA in power save mode to request data frames from an AP. A STA in power save mode can conserve battery power by periodically sleeping and waking up. When a STA sleeps, it cannot receive any data frames from the AP, so it informs the AP of its power save status by setting a bit in its MAC header. The AP then buffers any data frames destined for the sleeping STA until it wakes up. When a STA wakes up, it sends a PS-Poll frame to the AP, indicating its association ID and requesting any buffered data frames. The AP then responds with one or more data frames, followed by an ACK or BA frame from the STA. The other options are not correct, as they are types of 802.11 management frames. An Action frame is used to perform various management actions, such as spectrum management, QoS management, radio measurement, etc. A Beacon frame is used to advertise the presence and capabilities of an AP or BSS. An Authentication frame is used to establish or terminate an authentication relationship between a STA and an AP.
質問 # 125
Using the exhibit as a reference, answer the following.
STA1 sent a data frame to Mesh AP2 destined for a local file server on the same subnet with MAC address 00:11:22:33:44:55. Mesh AP2's mesh forwarding algorithm determined that the frame should be forwarded through Mesh AP1.
In the frame sent from Mesh AP2 to Mesh AP1, what is true of the contents of the MAC header?
(Choose 3)
- A. To DS = 0
- B. TA = STA1's MAC Address
- C. SA = Mesh AP2's MAC Address
- D. DA = 00:11:22:33:44:55
- E. RA = Mesh AP1's MAC Address
- F. From DS = 1
正解：D、E、F
質問 # 126
You have captured 802.11 traffic using an adapter that includes the radio tap header. You see several frames often called announcement frames in the capture.
What best describes these types of frames?
- A. They are meant to provide information to the network that may result in state changes, but they are not open for rejection
- B. They only include beacon and probe request frames
- C. They only include beacon and probe response frames
- D. They are used to allow a STA to awake from sleep and for no other reason
正解：C
質問 # 127
Shown is a screenshot of a wireless protocol analyzer displaying the decode information for a single 802.11 encrypted data + CF-Poll frame. The infrastructure BSS on which this information was captured is using WEP and this particular frame was sent from a client station (STA) to an access point (AP).
As a protocol analyst, how would you explain the existence of this frame on the wireless medium given the information in the decode?
- A. The frame was misinterpreted because of insufficient information received by the analyzer due to frame corruption.
- B. The IEEE 802.11 network is using both version 1 and version 2 protocols simultaneously. This unexpected frame is from the version 2 protocol set.
- C. The access point is operating as a repeater, and clients must poll repeater access points in order to transmit data frames through them.
- D. The frame was sent by a client station that does not comply with IEEE HR/DSSS standard to an access point that is Wi-Fi certified.
正解：A
質問 # 128
You are performing a multiple adapter channel aggregation capture to troubleshoot a VoIP roaming problem and would like to measure the roaming time from the last VoIP packet sent on the old AP's channel to the first VoIP packet sent on the new AP's channel. Which timing column in the packet view would measure this for you?
- A. Relative
- B. Absolute
- C. Delta
- D. Roaming
正解：D
解説：
The "Roaming" timing column specifically measures the time elapsed between the last packet on the old AP's channel and the first packet on the new AP's channel, providing valuable information about the roaming time in VoIP troubleshooting scenarios.
質問 # 129
As it relates to a spectrum analyzer, complete the following sentence.
The ____________ plot always displays the percentage of time (shown on the Y axis) that the overall RF power is a certain specified threshold (of amplitude) above the noise floor for a given frequency range (shown on the X axis).
- A. Swept Spectrogram
- B. Interferer Count
- C. FFT Duty Cycle
- D. Real-Time FFT
- E. SNR
正解：C
質問 # 130
Which piece of information is not transmitted in an HT PPDU header?
- A. MCS index
- B. PPDU length
- C. Number of Spatial Streams
- D. Channel number
正解：D
解説：
Explanation
The channel number is not transmitted in an HT PPDU header. An HT PPDU header is a part of the PPDU that contains information such as modulation, coding, data rate, and number of spatial streams for an 802.11n transmission. The channel number is not included in the HT PPDU header, as it is determined by the frequency band and channel width that are used by the transmitter and receiver. The channel number can be inferred from the frequency band and channel width, which are indicated by bits in different fields of the HT PPDU header, such as HT-SIG and HT-LTF. The other options are not correct, as they are transmitted in an HT PPDU header. The number of spatial streams, PPDU length, and MCS index are indicated by bits in the HT-SIG field of the HT PPDU header. References: [Wireless Analysis Professional Study Guide CWAP-404], Chapter 4: 802.11 Physical Layer, page 108-109
質問 # 131
When performing protocol analysis, you capture an 802.11ac data frame on channel 52, transmitted at MSC 8.
At what data rate was the PHY Preamble transmitted?
- A. 86.7 Mbps
- B. 54 Mbps
- C. 6 Mbps
- D. 78 Mbps
正解：C
解説：
The transmitter sends the preamble at 1 Mbps (802.11 or 802.11b DSSS) or 6 Mbps (802.11a or
802.11g ERP-OFDM).
Reference: http://mediA.techtarget.com/searchMobileComputing/downloads/CWAP_ch8.pdf
質問 # 132
Recently, three rogue APs have been connected to the network and later discovered. You want to prevent future rogue AP installations as much as possible.
What is the first step to eliminating or reducing rogue APs on the network?
- A. Define a direct policy that stipulates the ramifications of installing unauthorized devices
- B. Create a hash of the MAC addresses of all authorized devices and continually scan for non- matching hashes
- C. Enable rogue detection in the existing authorized APs
- D. Use IPSec between every AP and the network infrastructure
正解：C
質問 # 133
Which common feature of a Spectrum Analyzer would be the best to help you locate a non-
802.11 interference source?
- A. Location filter
- B. Max hold
- C. Device finder
- D. Waterfall plot
正解：C
解説：
The device finder is a common feature of a spectrum analyzer that helps locate a non-802.11 interference source. The device finder uses a directional antenna to measure the signal strength of a specific frequency or signal source. By pointing the antenna in different directions, the device finder can indicate the direction and distance of the interference source. The device finder can also filter out other signals that are not related to the interference source. The other options are not correct, as they do not help locate a non-802.11 interference source. Max hold and min hold are features that show the maximum and minimum RF power levels over time, respectively.
Location filter is a feature that filters out signals that are not from a specific location or area.
質問 # 134
You are repairing a misconfiguration in WMM settings on an AP.
The aCWmin and aCWmax values were all changed.
What is the default aCWmax for AC_BK?
- A. 0
- B. 1
- C. 2
- D. 3
正解：C
質問 # 135
Which parameters accurately describe the Beacon Interval field in the Beacon frame? (Choose 2)
- A. Indicates the exact time interval between Beacon transmissions
- B. Value can range from 0 to 2007
- C. 4-octet length
- D. Indicates the desired time interval between TBTTs
- E. easured in time units of 1024 µs
正解：D、E
質問 # 136
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