CWNP CWNP Certifications CWNA-108 Questions & Answers

• Question 161:

  You are troubleshooting a client issue on a Windows laptop. The laptop can see and connect to 2.4 GHz APs, but is does not even see 5 GHz APs. While evaluating the issue, you determine that this problem is happening for all of the laptops of this model in the organization. Several other tablets connect on channel 48 and channel 52 in the same work areas. What is the likely problem?

  A. The clients are configured to use WPA and 5 GHz channels only support WPA2.

  B. The client drivers are faulty and should be upgraded.

  C. The antennas in the laptop have insufficient gain to detect the 5 GHz signals.

  D. The access points are configured to disallow 5 GHz.

  Correct Answer: C

• Question 162:

  You are troubleshooting a client problem with a 2.4 GHz WLAN connection. The client is experiencing surprisingly low data rates during the work day. You analyze the workspace outside of business hours and detect a strong signal with a

  typical noise floor at the client location. During working hours, the user works with a laptop in the area and uses an external USB hard drive for continuous data access. The user also states that the laptop works as expected on her home

  network. The user working approximately 8 feet away from this client experiences no problems.

  Based on this information, what is the likely cause of the problem?

  A. The AP is overloaded during the work day

  B. The drivers in the laptop are corrupt

  C. The laptop has a failing wireless adapter

  D. The external hard drive is USB 3.0 and is causing a significant increase in the noise floor when in use

  Correct Answer: D

• Question 163:

  In addition to coverage analysis results, what should be included in a post-deployment site survey report to ensure WLAN users experience acceptable performance?

  A. WAN interface analysis results

  B. Capacity analysis results

  C. Application Layer protocol availability analysis results

  D. Layer 4 protocol availability analysis results

  Correct Answer: B

• Question 164:

  You have implemented an 802.11ax WLAN for a customer. All APs are four stream HE APs. The customer states that it is essential that most of the clients can use the OFDMA modulation scheme. What do you tell the customer?

  A. The clients that must support OFDMA must also be upgraded to 802.11ax

  B. OFDMA is an optional feature of 802.11ax and most APs don't even support it

  C. All 5 GHz PHYs use OFDM modulation, so you will achieve OFDMA everywhere in 5 GHz

  D. If the devices support 802.11ac, they can be updated to support OFDMA through driver upgrades

  Correct Answer: A

  OFDMA is a new modulation scheme introduced in 802.11ax that allows multiple users to share the same channel by dividing it into smaller subchannels called resource units (RUs). This improves the efficiency and capacity of the WLAN by reducing contention and overhead. However, to use OFDMA, both the AP and the client must support 802.11ax and negotiate the parameters of the subchannel allocation. Therefore, the customer needs to upgrade the clients that require OFDMA to 802.11ax devices12. The other options are not correct because they do not reflect the reality of OFDMA. Option B is incorrect because OFDMA is a mandatory feature of 802.11ax for both downlink and uplink transmissions, and all 802.11ax APs must support it1. Option C is incorrect because OFDM and OFDMA are different modulation schemes, and OFDM does not allow multiple users to share the same channel. Option D is incorrect because 802.11ac devices cannot support OFDMA through driver upgrades, as they lack the hardware and firmware capabilities to do so2. References: 1: CWNA-108 Official Study Guide, page 144 2: OFDMA

• Question 165:

  What feature of 802.1 lax (HE) may impact design decisions related to AP placement and the spacing between same-channel BSS cells (3SAs) because it is designed to reduce overlapping BSS contention?

  A. TWT

  B. BSS Color

  C. uplink MU-MIMO

  D. 6 GHz band support

  Correct Answer: B

• Question 166:

  You must plan for POE in an office environment. Which one of these devices is least likely to be a POE PSE?

  A. Midspan multi-port injector

  B. Switch

  C. VolP Phone

  D. Midspan injector

  Correct Answer: C

  A VoIP phone is least likely to be a POE PSE of the devices listed. POE stands for Power over Ethernet, which is a technology that allows devices to receive both power and data over a single Ethernet cable. A POE PSE stands for Power Sourcing Equipment, which is a device that provides power to other devices over Ethernet. A POE PD stands for Powered Device, which is a device that receives power from a PSE over Ethernet. A midspan multi- port injector, a switch, and a midspan injector are examples of POE PSEs, as they can supply power to multiple devices over Ethernet cables. A VoIP phone is an example of a POE PD, as it can receive power from a PSE over an Ethernet cable. However, some VoIP phones can also act as POE PSEs for other devices, such as IP cameras or wireless access points, but this is not very common. References: CWNA-109 Study Guide, Chapter 8: Wireless LAN Access Points, page 2411

• Question 167:

  What authentication method is referenced in the 802.11-2016 and 802.11-2020 specifications and is recommended for robust WI-AN client security?

  A. SSL

  B. 802.1X/EAP

  C. IPSec

  D. WEP

  Correct Answer: B

  The authentication method that is referenced in the 802.11-2016 and 802.11-2020 specifications and is recommended for robust WLAN client security is 802.1X/EAP. 802.1X/EAP stands for IEEE 802.1X Port- Based Network Access Control with Extensible Authentication Protocol and is a framework that provides strong authentication and dynamic encryption key generation for WLAN clients. 802.1X/EAP involves three parties: the supplicant (the client), the authenticator (the AP or the controller), and the authentication server (usually a RADIUS server). The supplicant sends its credentials (such as username and password, certificate, or token) to the authenticator, which forwards them to the authentication server. The authentication server verifies the credentials and sends a response to the authenticator, which grants or denies access to the supplicant. The authentication server also generates a master key that is used to derive encryption keys for the data frames between the supplicant and the authenticator. 802.1X/EAP supports various EAP methods that offer different levels of security and flexibility, such as EAP-TLS, EAPPEAP, EAP-TTLS, EAP-FAST, and EAP-SIM. SSL, IPSec, and WEP are not authentication methods, but rather encryption or security protocols that are not specific to WLANs or referenced in the 802.11 specifications. References: [CWNP Certified Wireless Network Administrator Official Study Guide: WNA-107], page 299; [CWNA: Certified Wireless Network Administrator Official Study Guide: WNA-106], page 289.

• Question 168:

  An AP is advertised as a tri-band, 4x4:4, Wi-Fi 6, 802. 11ax AP. Based on this information and assuming it is correctly advertised, what can be determined as certainly true about this AP?

  A. It supports four channels in 2.4 GHz and 4 channels in 5 GHz

  B. It supports UL-MU-MIMO

  C. It uses a modified OpenWRT firmware

  D. It has 4 radio chains

  Correct Answer: D

  Explanation: Based on the information given, what can be determined as certainly true about this AP is that it has 4 radio chains. A radio chain is a hardware component that consists of an antenna, a radio frequency (RF) amplifier, and a transceiver. The number of radio chains indicates how many spatial streams an AP can transmit or receive simultaneously using Multiple Input Multiple Output (MIMO) technology. The notation x:y:z in an AP specification denotes the number of radio chains (x), the number of spatial streams (y), and the number of spatial streams per band (z). Therefore, a tri-band, 4x4:4, Wi-Fi 6, 802.11ax AP has four radio chains in each of its three bands (2.4 GHz, low 5 GHz, and high 5 GHz). It also supports four spatial streams in total and four spatial streams per band. It cannot be determined as certainly true that it supports four channels in each band, UL-MU-MIMO, or uses a modified OpenWRT firmware based on the information given. References: [CWNP Certified Wireless Network Administrator Official Study Guide: WNA-107], page 223; [CWNA: Certified Wireless Network Administrator Official Study Guide: WNA-106], page 213.

• Question 169:

  A POE device requires 47 W of power. What POE specification should be used?

  A. 802.3at

  B. 802.3af

  C. 802.3bt

  D. 802. 11at

  Correct Answer: C

  A POE device that requires 47 W of power should use the 802.3bt specification. This is because 802.3bt is the latest POE standard that supports up to 90 W of power delivery over four pairs of wires in an Ethernet cable. The previous POE standards, such as 802.3af and 802.3at, only support up to 15.4 W and 30 W of power delivery over two pairs of wires in an Ethernet cable, respectively. Therefore, they are not sufficient for powering a device that requires 47 W of power. The 802.11at specification does not exist; it is a typo or confusion with the 802.3at specification. References: CWNA-109 Study Guide, Chapter 8: Wireless LAN Access Points, page 2431

• Question 170:

  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

  Correct Answer: A

  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: WNA-107], page 112; [CWNA: Certified Wireless Network Administrator Official Study Guide: WNA-106], page 102.