CWAP-404 Online Practice Questions and Answers

Correct Answer: B

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

Correct Answer: C

Explanation: Display filters are applied after the capture is completed and they only hide the packets from view. The filtered packets are still present in the capture file and can be enabled for view later by changing or removing the display filter.

This is an advantage over capture-time filters, which discard the packets that do not match the filter criteria and cannot be recovered later34 References:

CWAP-403 Study Guide, Chapter 2: Protocol Analysis, page 37 CWAP-403 Objectives, Section 2.3: Apply display filters

Correct Answer: A

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

Correct Answer: B

Explanation: When performing protocol analysis, you would look at the HT Information Element in the Beacon frame to determine which one of the four HT protection modes the AP is operating in. The HT Information Element contains various

subfields that provide information about the HT network configuration and operation. One of these subfields is the HT Protection field, which indicates whether any protection mechanisms are required for mixed-mode operation with non-HT

STAs. The four possible values for this field are:

No Protection: No protection mechanisms are required. Non-member Protection: RTS/CTS or CTS-to-self protection is required for all HT transmissions.

20 MHz Protection: RTS/CTS or CTS-to-self protection is required for all HT transmissions using a 40 MHz channel.

Non-HT Mixed Mode: All HT transmissions must use a non-HT preamble and header . References: CWAP-404 Certified Wireless Analysis Professional Study and Reference Guide, Chapter 11: 802.11n/ac/ax PHYsical Layer Frame

Exchanges, page 378; CWAP-404 Certified Wireless Analysis Professional Study and Reference Guide, Chapter 11: 802.11n/ac/ax PHYsical Layer Frame Exchanges, page 379.

Correct Answer: D

Explanation: A VoIP phone, using WMM Power Save, requests data frames buffered at the AP by transmitting a trigger frame, which is a QoS Null frame or a QoS Data frame. WMM Power Save is a power saving mode that allows a STA (station) to conserve battery power by periodically sleeping and waking up. WMM Power Save is based on WMM (Wi-Fi Multimedia), which is a QoS (Quality of Service) enhancement that provides prioritized and differentiated access to the medium fordifferent types of traffic. 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 trigger frame to the AP, indicating its AC (Access Category), which is a logical queue that corresponds to its QoS level. A trigger frame can be either a QoS Null frame or a QoS Data frame, depending on whether it has any payload or not. The AP then responds with one or more data frames from the same AC as the trigger frame, followed by an ACK or BA (Block Acknowledgement) frame from the STA. The other options are not correct, as they are not used by a VoIP phone using WMM Power Save to request data frames buffered at the AP. A PS-Poll (Power Save Poll) frame is used by a STA using legacy power save mode, not WMM Power Save mode, to request data frames buffered at the AP. A PS-Poll frame does not indicate any AC or QoS information. Setting the More Data bit in the MAC header to 1 does not request any data frames from the AP, but indicates that there are more data frames to be sent by the STA or received by the STA. Transmitting a WMM Action frame does not request any data frames from the AP, but performs various management actions related to WMM features, such as admission control, parameter update, etc. References: [Wireless Analysis Professional Study Guide CWAP-404], Chapter 7: QoS Analysis, page 198-199

Correct Answer: C

Explanation: The data rate at which the PHY preamble was transmitted is 6 Mbps. The PHY preamble is a part of the PPDU that is transmitted before the PHY header and the PSDU. The PHY preamble consists of a series of training fields that help the receiver to detect and synchronize with the signal. The PHY preamble is always transmitted at a fixed data rate that depends on the type of PPDU (e.g., OFDM, HT, VHT, HE). For an 802.1 lac data frame on channel 52, which uses VHT PPDUs, the data rate for the PHY preamble is 6 Mbps. This data rate does not depend on MCS (Modulation and Coding Scheme), which only affects the data rate for the PSDU. References: [Wireless Analysis Professional Study Guide CWAP-404], Chapter 4: 802.11 Physical Layer, page 99-100

Correct Answer: B

Explanation: 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. References: [Wireless Analysis Professional Study Guide], Chapter 3: Spectrum Analysis, page 74-75

Correct Answer: D

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

Correct Answer: B

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.

Correct Answer: A

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