Free CWAP-404 Braindumps Download Updated on Apr 19, 2024 with 62 Questions
CWNP CWAP-404 Exam Practice Test Questions
CWNP CWAP-404 Exam Topics:
| Section | Objectives |
|---|---|
Protocol Analysis - 15% | |
| Capture 802.11 frames using the appropriate methods | - Select capture devices
- Install monitor mode drivers |
| Understand and apply the common capture configuration parameters available in protocol analysis tools | - Save to disk - Packet slicing - Event triggers - Buffer options - Channels and channel widths - Capture filters - Channel scanning and dwell time |
| Analyze 802.11 frame captures to discover problems and find solutions | - Use appropriate display filters to view relevant frames and packets - Use colorization to highlight important frames and packets - Configure and display columns for analysis purposes - View frame and packet decodes while understanding the information shown and applying it to the analysis process - Use multiple adapters and channel aggregation to view captures from multiple channels - Implement protocol analyzer decryption procedures - View and use a capture’s statistical information for analysis - Use expert mode for analysis - View and understand peer maps as they relate to communications analysis |
| Utilize additional tools that capture 802.11 frames for analysis and troubleshooting | - WLAN scanners and discovery tools - Protocol capture visualization and analysis tools - Centralized monitoring, alerting, and forensic tools |
| Ensure appropriate troubleshooting methods are used with all analysis types | - Define the problem - Determine the scale of the problem - Identify probable causes - Capture and analyze the data - Observe the problem - Choose appropriate remediation steps - Document the problem and resolution |
Spectrum Analysis - 10% | |
| Capture RF spectrum data and understand the common views available in spectrum analyzers | - Install, configure, and use spectrum analysis software and hardware - Capture RF spectrum data using handheld, laptop-based, and infrastructure spectrum capture solutions - Understand and use spectrum analyzer views
|
| Analyze spectrum captures to identify relevant RF information and issues | - RF noise floor in an environment - Signal-to-Noise Ratio (SNR) for a given signal - Sources of RF interference and their locations - RF channel utilization - Non-Wi-Fi transmitters and their impact on WLAN communications - Overlapping and non-overlapping adjacent channel interference - Poor performing or faulty radios |
| Analyze spectrum captures to identify various device signatures | - Identify various 802.11 PHYs
- Identify non-802.11 devices based on RF behaviors and signatures
|
| Use centralized spectrum analysis solutions | - AP-based spectrum analysis - Sensor-based spectrum analysis |
PHY Layers and Technologies - 10% | |
| Understand and describe the functions of the PHY layer and the PHY protocol data units (PPDUs) | - DSSS (Direct Sequence Spread Spectrum) - HR/DSSS (High Rate/Direct Sequence Spread Spectrum) - OFDM (Orthogonal Frequency Division Multiplexing) - ERP (Extended Rate PHY) - HT (High Throughput) - VHT (Very High Throughput) - HE (High Efficiency)
|
| Apply the understanding of PHY technologies, including PHY headers, preambles, training fields, frame aggregation, and data rates, to captured data | |
| Identify and use PHY information provided within pseudo-headers in protocol analyzers | - Pseudo-Header formats
- Key pseudo-header content
|
| Recognize the limits of protocol analyzers to capture PHY information including NULL data packets and PHY headers | |
| Use appropriate capture devices based on proper understanding of PHY types | - Supported PHYs - Supported spatial streams |
MAC Sublayer and Functions - 25% | |
| Understand frame encapsulation and frame aggregation | - Frame aggregation (A-MSDU and A-MPDU) |
NEW QUESTION # 15
In a Spectrum Analyzer the Swept Spectrogram plot displays what information?
- A. RF power present at a particular frequency over the course of time
- B. Reductions in frame transmissions
- C. Wi-Fi Device information
- D. The RF time domain
Answer: A
Explanation:
Explanation
The Swept Spectrogram plot is a spectrum analysis plot that shows the RF power present at a particular frequency over the course of time. It can help identify trends and patterns in the RF spectrum over a longer period of time. It can also show how the RF environment changes over time and how different sources of RF signals affect each other. The other options are not correct, as they describe different types of plots or information that are not related to the Swept Spectrogram plot. References: [Wireless Analysis Professional Study Guide], Chapter 3: Spectrum Analysis, page 72-73
NEW QUESTION # 16
Which one of the following is required for Wi-Fi integration in laptop-based Spectrum Analyzer software in addition to the spectrum analysis adapter?
- A. A firmware upgrade for the spectrum analysis adapter
- B. SNMP read credentials to the WLAN controller or APs
- C. A directional antenna
- D. An 802.11 wireless adaptor
Answer: D
Explanation:
Explanation
An 802.11 wireless adaptor is required for Wi-Fi integration in laptop-based spectrum analyzer software in addition to the spectrum analysis adapter. The spectrum analysis adapter is a hardware device that captures the RF signals in the wireless environment and sends them to the spectrum analyzer software for analysis and display. The 802.11 wireless adapter is a hardware device that connects the laptop to the wireless network and allows the spectrum analyzer software to correlate the RF data with the Wi-Fi data, such as SSID, channel, and BSSID. This enables the spectrum analyzer software to provide more context and insight into the spectrum activity and its impact on the Wi-Fi network. A firmware upgrade for the spectrum analysis adapter is not required for Wi-Fi integration, but it may be needed to fix bugs or add features to the device. A directional antenna is an antenna that focuses the RF energy in a specific direction and has a high gain and a narrow beamwidth. A directional antenna can be used with a spectrum analysis adapter to pinpoint the location or source of interference or noise in the wireless environment, but it is not required for Wi-Fi integration. SNMP read credentials to the WLAN controller or APs are not required for Wi-Fi integration, but they may be useful for obtaining additional information about the wireless network configuration and performance from the network devices.References:
CWAP-404 Study Guide, Chapter 4: Spectrum Analysis and Troubleshooting, page 123 CWAP-404 Objectives, Section 4.2: Integrate Wi-Fi data with spectrum analysis data CWAP-404 Study Guide, Chapter 4: Spectrum Analysis and Troubleshooting, page 131
NEW QUESTION # 17
Which one of the statements regarding the Frame Control field in an 802.11 MAC header is true?
- A. The Frame Control field contains subfields, and soma in 1-bit flags
- B. The Frame Control field is always set to 0
- C. Only Control frames have a Frame Control field
- D. The Frame Control field is used to communicate the duration value
Answer: A
Explanation:
Explanation
The statement that the Frame Control field contains subfields, and some 1-bit flags is true. The Frame Control field is a 2-byte field in the MAC header that contains information about the type, subtype, and characteristics of a frame. The Frame Control field is divided into several subfields, each with a specific function and length.
Some of these subfields are 1-bit flags, which can be set to 0 or 1 to indicate a certain condition or status. For example, the To DS and From DS subfields are 1-bit flags that indicate whether a frame is destined for or originated from the DS (Distribution System). The other statements are not true, as they do not describe the Frame Control field correctly. All types of frames (management, control, and data) have a Frame Control field, not just control frames. The Frame Control field is not used to communicate the duration value, which is a separate field in the MAC header. The Frame Control field is not always set to 0, as it varies depending on the type, subtype, and characteristics of each frame. References: [Wireless Analysis Professional Study Guide CWAP-404], Chapter 5: 802.11 MAC Sublayer, page 113-114
NEW QUESTION # 18
What interframe space would be expected between a CIS and a Data frame?
- A. SIFS
- B. AIFS
- C. PIFS
- D. DIFS
Answer: A
Explanation:
Explanation
The interframe space that would be expected between a CTS (Clear to Send) and a Data frame is SIFS (Short Interframe Space). A SIFS is the shortest interframe space that is used for high-priority transmissions, such as ACKs (Acknowledgements), CTSs, or data frames that are part of a fragmentation or aggregation process. A SIFS is a fixed value that depends on the PHY type and channel width. A CTS and a Data frame are part of a virtual carrier sense mechanism called RTS/CTS (Request to Send/Clear to Send), which is used to avoid collisions and hidden node problems in wireless transmissions. When a STA (station) wants to send a data frame, it first sends an RTS frame to the intended receiver, indicating the duration of the transmission. The receiver then responds with a CTS frame, also indicating the duration of the transmission. The other STAs in the vicinity hear either the RTS or the CTS frame and update their NAV (Network Allocation Vector) timers accordingly, deferring their access to the medium until the transmission is over. The sender then sends the data frame after waiting for a SIFS, followed by an ACK frame from the receiver after another SIFS. The other options are not correct, as they are not used between a CTS and a Data frame. A PIFS (PCF Interframe Space) is used for medium access by the PCF (Point Coordination Function), which is an optional and rarely implemented polling-based mechanism that provides contention-free service for time-sensitive traffic. An AIFS (Arbitration Interframe Space) is used for medium access by different ACs (Access Categories), which are logical queues that correspond to different QoS (Quality of Service) levels for different types of traffic. An AIFS is a variable interframe space that depends on the AIFSN (Arbitration Interframe Space Number) value of each AC. A DIFS (Distributed Interframe Space) is used for medium access by the DCF (Distributed Coordination Function), which is the default and mandatory contention-based mechanism that provides best-effort service for normal traffic. References: [Wireless Analysis Professional Study Guide CWAP-404], Chapter 6: 802.11 Frame Exchanges, page 166-167; Chapter 7: QoS Analysis, page 194-195
NEW QUESTION # 19
ABC International has installed a new smart ZigBee controlled lighting system. However, the network team is concerned that this new system will interfere with the existing WLAN and has asked you to investigate the impact of the two systems operating simultaneously in the 2.4 GHz band. When performing Spectrum Analysis, which question could you answer by looking at the FFT plot?
- A. Is the ZigBee system causing an increase in WLAN retries?
- B. Is the ZigBee system using more than 50% of the available airtime?
- C. Is the WLAN corrupting ZigBee system messages?
- D. Do the ZigBee channels used by the lighting system overlap with the WLAN channels?
Answer: D
Explanation:
Explanation
The FFT plot is a spectrum analysis plot that shows the RF power present at a particular frequency over a short period of time. It can help identify the sources and characteristics of RF signals in the spectrum. By looking at the FFT plot, you can determine which ZigBee channels are used by the lighting system and whether they overlap with the WLAN channels in the 2.4 GHz band. ZigBee channels are 5 MHz wide and WLAN channels are 20 MHz or 40 MHz wide, so there is a possibility of overlap and interference between them. The other questions cannot be answered by looking at the FFT plot alone, as they require other types of plots or analysis tools, such as duty cycle plot, airtime utilization plot, or protocol analyzer. References: [Wireless Analysis Professional Study Guide], Chapter 3: Spectrum Analysis, page 69-70
NEW QUESTION # 20
How many frames make up the Group Key Handshake excluding any Ack frames that may be required?
- A. 0
- B. 1
- C. 2
- D. 3
Answer: B
Explanation:
Explanation
The Group Key Handshake consists of two frames excluding any Ack frames that may be required. The Group Key Handshake is used to distribute and update the Group Temporal Key (GTK) for encrypting broadcast and multicast traffic. The AP initiates the Group Key Handshake by sending a Group Key Message 1 frame to a STA, which contains the new GTK and other information. The STA responds with a Group Key Message 2 frame to the AP, which confirms the receipt of the GTK and other information. After this, both the AP and the STA can use the new GTK for encryption and decryption of broadcast and multicast traffic . References:
CWAP-404 Certified Wireless Analysis Professional Study and Reference Guide, Chapter 7: 802.11 Security, page 246; CWAP-404 Certified Wireless Analysis Professional Study and Reference Guide, Chapter 7: 802.11 Security, page 247.
NEW QUESTION # 21
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 customer should replace all their Bluetooth wireless mice as they are stopping the users on floor 5 from connecting to the wireless network
- B. 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
- C. The customers APs are misbehaving and a technical support case should be open with the vendor
- D. 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
Answer: D
Explanation:
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.
NEW QUESTION # 22
Which one of the following should be the first step when troubleshooting a WLAN issue?
- A. Identify probable causes
- B. Identify capture locations
- C. Define the problem
- D. Perform an initial WLAN scan and see if any obvious issues stand out
Answer: C
Explanation:
Explanation
The first step in any troubleshooting process is to define the problem. This involves gathering information from various sources, such as users, network administrators, network documentation, and network monitoring tools. Defining the problem helps to narrow down the scope of the issue and identify the symptoms, causes, and effects of the problem12 References:
CWAP-403 Study Guide, Chapter 1: Troubleshooting Methodology, page 7
CWAP-403 Objectives, Section 1.1: Define the problem
NEW QUESTION # 23
Finish the statement:
It is possible to distinguish between_______22 MHz transmissions and________20 MHz transmissions when looking at an FFT plot.
- A. ERP and VHT
- B. HT and VHT
- C. OFDM and HT
- D. HR/DSSS and ERP
Answer: C
Explanation:
Explanation
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. References: [Wireless Analysis Professional Study Guide CWAP-404], Chapter 3: Spectrum Analysis, page 70-71
NEW QUESTION # 24
Which one of the following statements is not true concerning DTIMs?
- A. Every Beacon frame must contain a DTIM
- B. The DTIM interval can dictate when an STA will wake up to listen to beacon frames
- C. Buffered Broadcast and Multicast traffic will be transmitted following a DTIM
- D. DTIM stands for Delivery Traffic Indication Map
Answer: A
Explanation:
Explanation
Every Beacon frame must contain a DTIM is not a true statement concerning DTIMs. DTIM stands for Delivery Traffic Indication Message, and it is a subfield within the TIM (Traffic Indication Map) element in a Beacon frame. The DTIM indicates how many Beacon frames (including the current one) will appear before the next DTIM. For example, if the DTIM interval is set to 3, it means that every third Beacon frame will contain a DTIM. Buffered broadcast and multicast traffic will be transmitted following a DTIM, so that STAs in power save mode can wake up and receive them. The DTIM interval can also dictate when an STA will wake up to listen to Beacon frames, as some STAs may choose to only listen to Beacon frames that contain a DTIM . References: CWAP-404 Certified Wireless Analysis Professional Study and Reference Guide, Chapter
6: MAC Sublayer Frame Exchanges, page 200; CWAP-404 CertifiedWireless Analysis Professional Study and Reference Guide, Chapter 6: MAC Sublayer Frame Exchanges, page 201.
NEW QUESTION # 25
Where would you look in a packet trace file to identify the configured Minimum Basic Rate (MBR) of a BSS?
- A. In the MBR Action frame
- B. Supported Rates & Extended Supported Rates elements in a Beacon frame
- C. In the MBR Information Element in an Association Response frame
- D. In the Minimum Basic Rate Element in a Beacon frame
Answer: B
Explanation:
Explanation
The configured Minimum Basic Rate (MBR) of a BSS can be identified by looking at the Supported Rates and Extended Supported Rates elements in a Beacon frame. A Beacon frame is a type of management frame that is transmitted by an AP to advertise its presence and capabilities to potential clients. A Beacon frame contains various information elements (IEs) that provide details about the BSS configuration and operation. The Supported Rates andExtended Supported Rates IEs list the data rates that are supported by the AP for data transmission. The MBR is the lowest data rate among these supported rates that is required for all clients to join and communicate with the BSS. The MBR is usually marked with a flag bit in these IEs to indicate its mandatory status. The other options are not correct, as they do not exist or do not indicate the MBR of a BSS. References: [Wireless Analysis Professional Study Guide CWAP-404], Chapter 5: 802.11 MAC Sublayer, page 123-124
NEW QUESTION # 26
How many frames are exchanged for 802.11 authentication in the 6 GHz band when WPA3-Enterprise is not used, and a passphrase is used instead?
- A. 0
- B. 1
- C. 2
- D. 3
Answer: B
Explanation:
Explanation
Two frames are exchanged for 802.11 authentication in the 6 GHz band when WPA3-Enterprise is not used, and a passphrase is used instead. Authentication is a process that establishes an identity relationship between a STA (station) and an AP (access point) before joining a BSS (Basic Service Set). There are two types of authentication methods defined by 802.11: Open System Authentication and Shared Key Authentication. Open System Authentication does not require any credentials or security information from a STA to join a BSS, and it consists of two frames: an Authentication Request frame sent by the STA to the AP, and an Authentication Response frame sent by the AP to the STA. Shared Key Authentication requires a shared secret key from a STA to join a BSS, and it consists of four frames: two challenge-response frames in addition to the request-response frames. However, Shared Key Authentication uses WEP (Wired Equivalent Privacy) as its encryption algorithm, which is insecure and deprecated. In the 6 GHz band, which is a newly available frequency band for WLANs, Shared Key Authentication is prohibited by the 802.11 standard, as it poses security and interference risks for other users and services in the band. The 6 GHz band requires all WLANs to use WPA3-Personal or WPA3-Enterprise encryption methods, which are more secure and robust than previous encryption methods such as WPA2 or WEP. WPA3-Personal uses a passphrase to derive a PMK (Pairwise Master Key), while WPA3-Enterprise uses an authentication server to obtain a PMK. Both methods use SAE (Simultaneous Authentication of Equals) as their authentication protocol, which replaces PSK (Pre-Shared Key) or EAP (Extensible Authentication Protocol). SAE consists of two frames: an SAE Commit frame sent by both parties to exchange elliptic curve parameters and nonces, and an SAE Confirm frame sent by both parties to verify each other's identities and generate a PMK. Therefore, when WPA3-Enterprise is not used, and a passphrase is used instead in the 6 GHz band, only two frames are exchanged for 802.11 authentication:
an SAECommit frame and an SAE Confirm frame. References: [Wireless Analysis Professional Study Guide CWAP-404], Chapter 8: Security Analysis, page 220-221
NEW QUESTION # 27
You are analyzing a packet decode of a Probe Request and notice the SSID element has a length of zero. What do you conclude about the transmitting STA?
- A. The WLAN adaptor is configured in promiscuous mode
- B. The STA is discovering a list of available BSSs
- C. The STA's WLAN adaptor is disabled
- D. The STA is operating in Ad-Hoc mode
Answer: B
Explanation:
Explanation
The STA is discovering a list of available BSSs by sending a Probe Request with an empty SSID element.
This is also known as a broadcast Probe Request, as it does not specify any particular SSID to probe for. Any AP that receives this Probe Request will respond with a Probe Response containing its own SSID and other information about its BSS. This way, the STA can learn about all the BSSs in its vicinity and choose which one to associate with . References: CWAP-404 Certified Wireless Analysis Professional Study and Reference Guide, Chapter 6: MAC Sublayer Frame Exchanges, page 191; CWAP-404 Certified Wireless Analysis Professional Study and Reference Guide, Chapter 6: MAC Sublayer Frame Exchanges, page 193.
NEW QUESTION # 28
Where, in a protocol analyzer, would you find an indication that a frame was transmitted as part of an A-MPDU?
- A. A-MPDU flag in the Frame Control Field
- B. A-MPDU flag in the QoS Control Field
- C. The HT Operation Element
- D. The Aggregation flag in the Radio Tap Header
Answer: D
Explanation:
Explanation
In a protocol analyzer, you would find an indication that a frame was transmitted as part of an A-MPDU by looking at the Aggregation flag in the Radio Tap Header. The Radio Tap Header is a pseudo-header that is added by some wireless capture devices to provide additional information about the physical layer characteristics of a frame. The Aggregation flag is one of the fields in this header, and it indicates whether the frame belongs to an A-MPDU or not. If the flag is set to 1, it means that the frame is part of an A-MPDU; if it is set to 0, it means that the frame is not part of an A-MPDU . References: CWAP-404 Certified Wireless Analysis Professional Study and Reference Guide, Chapter 9: PHY Layer Frame Formats andTechnologies, page 303; CWAP-404 Certified Wireless Analysis Professional Study and Reference Guide, Chapter 9: PHY Layer Frame Formats and Technologies, page 304.
NEW QUESTION # 29
An RTS frame should be acknowledged by which frame?
- A. Block Ack
- B. RTS-Ack
- C. CTS
- D. Ack
Answer: C
Explanation:
Explanation
An RTS (Request to Send) frame should be acknowledged by a CTS (Clear to Send) frame. An RTS and CTS frame are types of control frames that are used to implement a virtual carrier sense mechanism called RTS/CTS. RTS/CTS is a technique that helps to avoid collisions and hidden node problems in wireless transmissions. When a STA (station) wants to send a data frame, it first sends an RTS frame to the intended receiver, indicating the duration of the transmission. The receiver then responds with a CTS frame, also indicating the duration of the transmission. The other STAs in the vicinity hear either the RTS or the CTS frame and update their NAV (Network Allocation Vector) timers accordingly, deferring their access to the medium until the transmission is over. The sender then sends the data frame, followed by an ACK (Acknowledgement) frame from the receiver. The other options are not correct, as they are not used to acknowledge an RTS frame. An ACK frame is used to acknowledge a data frame, not an RTS frame. An RTS-Ack frame does not exist, as there is no such type of control frame in 802.11. A Block Ack (BA) frame is used to acknowledge multiple data frames in a single frame, not an RTS frame. References: [Wireless Analysis Professional Study Guide CWAP-404], Chapter 6: 802.11 Frame Exchanges, page 166-167
NEW QUESTION # 30
802.11k Neighbor Requests and Neighbor Reports are sent in what type of Management Frames?
- A. RRM
- B. Reassociation Request and Reassociation Response
- C. Beacon
- D. Action
Answer: D
Explanation:
Explanation
802.11k Neighbor Requests and Neighbor Reports are sent in Action frames. An Action frame is a Management frame that is used to perform various operations or functions related to the operation or maintenance of a wireless network. An Action frame consists of a Category field that indicates the type of action being performed, and a variable-length Action Details field that contains specific information related to the action. For example, an Action frame with a Category field value of 5 indicates a Radio Measurement action, and the Action Details field may contain a Neighbor Request or a Neighbor Report subelement .
References: CWAP-404 CertifiedWireless Analysis Professional Study and Reference Guide, Chapter 6: MAC Sublayer Frame Exchanges, page 207; CWAP-404 Certified Wireless Analysis Professional Study and Reference Guide, Chapter 6: MAC Sublayer Frame Exchanges, page 208; CWAP-404 Certified Wireless Analysis Professional Study and Reference Guide, Chapter 12: 802.11k/v/r/u/w/ai Amendments, page 434.
NEW QUESTION # 31
In which element of a Beacon frame would you look to identity the current HT protection mode in which an AP is operating?
- A. HT Operations Element
- B. ERP Information Element
- C. HT Protection Element
- D. HT Capabilities Element
Answer: A
Explanation:
Explanation
The HT protection mode in which an AP is operating can be identified by looking at the HT Operations element in a Beacon frame. The HT Operations element is a part of the Beacon frame that contains information about the High Throughput (HT) capabilities and operation of an 802.11n BSS. The HT Operations element has a field called HT Protection, which indicates how the BSS protects its HT transmissions from interference or collisions with non-HT devices or BSSs. The HT Protection field can have four values: No Protection, Nonmember Protection, 20 MHz Protection, or Non-HT Mixed Mode. The other options are not correct, as they do not contain information about the HT protection mode. The HT Protection element does not exist, the ERP Information element is used for Extended Rate PHY (ERP) protection mode for 802.11g devices, and the HT Capabilities element is used for indicating the supported HT features of an individual device. References: [Wireless Analysis Professional Study Guide CWAP-404], Chapter 5: 802.11 MAC Sublayer, page 125-126
NEW QUESTION # 32
You are troubleshooting a client that is experiencing slow WLAN performance. As part of the troubleshooting activity, you start a packet capture on your laptop close to the client device. While analyzing the packets, you suspect that you have not captured all packets transmitted by the client. By analyzing the trace file, how can you confirm if you have missing packets?
- A. Protocol Analyzers show the number of missing packets in their statistics view
- B. The missing packets will be shown as CRC errored packets
- C. Look for gaps in the sequence number in MAC headers.
- D. Retransmission are an indication of missing packets
Answer: C
Explanation:
Explanation
One way to confirm if you have missing packets in your packet capture is to look for gaps in the sequence number in MAC headers. The sequence number is a 12-bit field in the MAC header that is used to identify and order data frames within a traffic stream. The sequence number is incremented by one for each new data frame transmitted by a STA, except for retransmissions, fragments, and control frames. The sequence number can range from 0 to 4095, and then wraps around to 0. If you see a jump or a gap in the sequence number between two consecutive data frames from the same STA, it means that you have missed some packets in between. The other options are not correct, as they do not confirm if you have missing packets in your packet capture. CRC errored packets are packets that have been corrupted during transmission and have failed the error detection check. Protocol analyzers may show the number of CRC errored packets in their statistics view, but not the number of missing packets. Retransmissions are an indication of packet loss or collision, but not necessarily of missing packets in your capture. References: [Wireless Analysis Professional Study Guide CWAP-404], Chapter 5: 802.11 MAC Sublayer, page 114-115
NEW QUESTION # 33
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