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NEW QUESTION # 89
You are troubleshooting throughput problems for a WLAN cell. The cell is provisioned with an
802.11ac dual-band AP. Users connected with both 5 GHz and 2.4 GHz connections are reporting performance problems. The AP settings are properly optimized. No interface issues have been detected (either co- channel interference or non-Wi-Fi interference) and the number of associated users is low.
What should you analyze to resolve the issue?
- A. the Ethernet uplink and the network infrastructure
- B. The 2.4 GHz radio configuration
- C. The 5 GHz radio configuration
- D. The antennas used on the client devices
Answer: A
NEW QUESTION # 90
Prior to a retransmission what happens to the CWmax value?
- A. Increases by 1
- B. Doubles and increases by 1
- C. Set to the value of the AIFSN
- D. Reset to 0
Answer: B
Explanation:
Before a retransmission, the CWmax (Contention Window maximum) value doubles and increases by 1. The CWmax is a parameter that determines the upper limit of the random backoff time that a STA (station) has to wait before attempting to access the medium. The random backoff time is chosen from a range of values between CWmin (Contention Window minimum) and CWmax. The CWmin and CWmax values depend on the AC (Access Category) of the traffic and the PHY type of the STA. If a transmission fails due to a collision or an error, the STA has to retransmit the frame after waiting for another random backoff time. However, to reduce the probability of another collision, the STA increases its CWmax value by doubling it and adding 1.
This increases the range of possible backoff values and spreads out the STAs more evenly. The STA resets its CWmax value to its original value after a successful transmission or after reaching a predefined limit.
NEW QUESTION # 91
Which one of the statements regarding the Frame Control field in an 802.11 MAC header is true?
- A. The Frame Control field contains three sub-fields and eight one-bit flags
- B. The Frame Control field is used to communicate the duration value
- C. Only Control frames have a Frame Control field
- D. The Frame Control field is always set to 0
Answer: D
Explanation:
This field is simply used to indicate which protocol version of 802.11 is being used by the frame.
This is always set to "0"
Reference: https://mrncciew.com/2014/09/27/cwap-mac-header-frame-control/
NEW QUESTION # 92
Many access points support IEEE 802.1Q VLAN tagging. When analyzing a WLAN system using IEEE 802.1Q tags, where can the VLAN tag number be seen?
- A. In the Sequence Control field of the MSDU
- B. In the Frame Control field of the MPDU header
- C. In the PLCP header's Service field
- D. In the Ethernet header on the wired port of the access point
- E. In the Beacon Management frame's Capabilities fixed field
Answer: D
NEW QUESTION # 93
When configuring a long term, forensic packet capture and saving all packets to disk which of the following is not a consideration?
- A. Real-time packet decodes
- B. Total capture storage space
- C. Analyzer location
- D. Individual trace file size
Answer: A
Explanation:
Real-time packet decodes are not a consideration when configuring a long-term, forensic packet capture and saving all packets to disk. Real-time packet decodes are useful for live analysis and troubleshooting, but they consume CPU and memory resources that could affect the performance of the capture process. For a long-term, forensic packet capture, it is more important to consider the analyzer location, the total capture storage space, and the individual trace file size. These factors affect the quality and quantity of the captured packets and the ease of post-capture analysis.
NEW QUESTION # 94
When a 5 GHz HT station in a 40 MHz BSS desires to protect a 40 MHz transmission from an OFDM station using an RTS/CTS or CTS-to-Self exchange, what frame format is used for the RTS and/or CTS frames?
- A. Phased Coexistence PPDU
- B. Dual-CTS
- C. HT-mixed format
- D. HT-greenfield format
- E. Non-HT Duplicate
Answer: E
NEW QUESTION # 95
What is the function of 802.11 Management frames?
- A. Prioritize network administration traffic
- B. Communicate configuration changes between WLAN controller and APs
- C. Manage the flow of data
- D. Manage the BSS
Answer: D
Explanation:
The function of 802.11 management frames is to manage the BSS. A BSS (Basic Service Set) is a group of STAs (stations) that share a common SSID (Service Set Identifier) and communicate with each other through an AP (access point) or directly in an ad hoc mode. Management frames are one of the three types of 802.11 frames, along with control and data frames. Management frames are used to establish, maintain, and terminate associations between STAs and APs, as well as to advertise and discover BSSs, exchange security information, report errors, and perform other management functions. The other options are not correct, as they are not functions of
802.11 management frames. Prioritizing network administration traffic, communicating configuration changes between WLAN controller and APs, and managing the flow of data are functions of other types of frames or protocols.
NEW QUESTION # 96
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. DTIM stands for Delivery Traffic Indication Map
- D. Buffered Broadcast and Multicast traffic will be transmitted following a DTIM
Answer: A
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.
NEW QUESTION # 97
The To DS bit is set to 0 and the From DS is set to 1.
What best describes this 802.11 frame?
- A. A frame being transmitted in a mesh BSS
- B. A frame being transmitted from an AP to a client STA
- C. A frame being transmitted from a client STA to an AP
- D. A frame being transmitted directly from one client STA to another
Answer: B
NEW QUESTION # 98
Where, in a protocol analyzer, would you find an indication that a frame was transmitted as part of an AMPDU?
- A. The HT Operation Element
- B. The Aggregation flag in the Radio Tap Header
- C. A-MPDU flag in the HT Control Field
- D. A-MPDU flag in the Frame Control Field
Answer: B
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.
NEW QUESTION # 99
Prior to a retransmission what happens to the CWmax value?
- A. Increases by 1
- B. Doubles and increases by 1
- C. Set to the value of the AIFSN
- D. Reset to 0
Answer: B
Explanation:
Explanation
Before a retransmission, the CWmax (Contention Window maximum) value doubles and increases by 1. The CWmax is a parameter that determines the upper limit of the random backoff time that a STA (station) has to wait before attempting to access the medium. The random backoff time is chosen from a range of values between CWmin (Contention Window minimum) and CWmax. The CWmin and CWmax values depend on the AC (Access Category) of the traffic and the PHY type of the STA. If a transmission fails due to a collision or an error, the STA has to retransmit the frame after waiting for another random backoff time. However, to reduce the probability of another collision, the STA increases its CWmax value by doubling it and adding 1.
This increases the range of possible backoff values and spreads out the STAs more evenly. The STA resets its CWmax value to its original value after a successful transmission or after reaching a predefined limit. References: [Wireless Analysis Professional Study Guide CWAP-404], Chapter 7: QoS Analysis, page
196-197
NEW QUESTION # 100
What is the formula used to calculate the Duration field value in an RTS frame?
- A. RTS Duration field = Data or management frame to be sent duration + CTS duration
- B. RTS Duration field = CTS duration
- C. RTS Duration field = Data or management frame to be sent duration + CTS duration + one ACK duration + three SIFS
- D. RTS Duration field = Data or management to be sent frame duration
Answer: C
NEW QUESTION # 101
Which one of the following is not a valid acknowledgement frame?
- A. Block Ack
- B. Ack
- C. RTS
- D. CTS
Answer: C
Explanation:
Explanation
RTS is not a valid acknowledgement frame. RTS stands for Request To Send, and it is a control frame that is used to initiate an RTS/CTS exchange before sending a data frame. The purpose of an RTS/CTS exchange is to reserve the medium for a data transmission and avoid collisions with hidden nodes. An acknowledgement frame is a control frame that is used to confirm the successful reception of a data frame or a block of data frames. The valid acknowledgement frames are CTS (Clear To Send), Ack (Acknowledgement), and Block Ack (Block Acknowledgement) . References: CWAP-404 Certified Wireless Analysis Professional Study and Reference Guide, Chapter 6: MAC Sublayer Frame Exchanges, page 186; CWAP-404 Certified Wireless Analysis Professional Study and Reference Guide, Chapter 6: MAC Sublayer Frame Exchanges, page 187; CWAP-404 Certified Wireless Analysis Professional Study and Reference Guide, Chapter 6: MAC Sublayer Frame Exchanges, page 189; CWAP-404 Certified Wireless Analysis Professional Study and Reference Guide, Chapter 6: MAC Sublayer Frame Exchanges, page 190.
NEW QUESTION # 102
When using Wireshark for protocol analysis, what filter will allow you to see only beacon frames?
- A. wlan.fc.type_subtype = =0x0b
- B. wlan.fc.type_subtype = =0x05
- C. wlan.fc.type_subtype = =0x04
- D. wlan.fc.type_subtype = =0x08
Answer: D
NEW QUESTION # 103
Given: Shown are frames captured from an IEEE 802.1X/LEAP authentication.
This WLAN is a Robust Security Network (RSN) using the CCMP cipher suite.
Using the information given in the screenshot, calculate how long it takes for only the frames that are part of the 4-Way handshake to complete.
- A. 210.443 ms
- B. 237.753 ms
- C. 243.743 ms
- D. 3.018 ms
- E. 5.820 ms
Answer: E
NEW QUESTION # 104
The PHY layer provides framing by adding a header to create what type of data unit?
- A. MPDU
- B. PPDU
- C. PSDU
- D. MSDU
Answer: B
Explanation:
Explanation
The PHY layer provides framing by adding a header to create a PPDU. 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 (PHY Service Data Unit) and a PHY header, which contains information such as modulation, coding, and data rate. The PHY layer adds the PHY header to the PSDU to create a PPDU for transmission, or removes the PHY header from the PPDU to extract the PSDU for reception. The other options are not correct, as they are not created by adding a header at the PHY layer. An MPDU (MAC Protocol Data Unit) is created by adding a MAC header and FCS to an MSDU (MAC Service Data Unit) at the MAC layer. An MSDU is the data unit that is passed from the LLC sublayer to the MAC sublayer or vice versa. References: [Wireless Analysis Professional Study Guide CWAP-404], Chapter 4: 802.11 Physical Layer, page 97-98
NEW QUESTION # 105
An RST frame should be acknowledged by which frame?
- A. Block Ack
- B. Ack
- C. RTS-Ack
- D. CTS
Answer: D
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.
NEW QUESTION # 106
What is the function of 802.11 Management frames?
- A. Prioritize network administration traffic
- B. Communicate configuration changes between WLAN controller and APs
- C. Manage the flow of data
- D. Manage the BSS
Answer: D
Explanation:
Explanation
The function of 802.11 management frames is to manage the BSS. A BSS (Basic Service Set) is a group of STAs (stations) that share a common SSID (Service Set Identifier) and communicate with each other through an AP (access point) or directly in an ad hoc mode. Management frames are one of the three types of 802.11 frames, along with control and data frames. Management frames are used to establish, maintain, and terminate associations between STAs and APs, as well as to advertise and discover BSSs, exchange security information, report errors, and perform other management functions. The other options are not correct, as they are not functions of 802.11 management frames. Prioritizing network administration traffic, communicating configuration changes between WLAN controller and APs, and managing the flow of data are functions of other types of frames or protocols. References: [Wireless Analysis Professional Study Guide CWAP-404], Chapter 5: 802.11 MAC Sublayer, page 120-121
NEW QUESTION # 107
The Retry subfield is found in which IEEE 802.11 frame field?
- A. Sequence Control field
- B. Data Control field
- C. Protocol Order field
- D. MAC Service Data Unit field
- E. Frame Control field
- F. QoS Control field
Answer: E
NEW QUESTION # 108
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 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
- B. The customer should replace all their Bluetooth wireless mice as they are stopping the users on floor 5 from connecting to the wireless network
- C. The customers APs are misbehaving and a technical support case should be open with the vendor
- 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
Answer: A
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 # 109
What interframe space would be expected between a CIS and a Data frame?
- A. DIFS
- B. AIFS
- C. SIFS
- D. PIFS
Answer: C
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 # 110
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