CWNP CWNA-109 Online Practice Questions and Exam Preparation

CWNP CWNA-109 Online Questions & Answers

• Question 111:

  A non-802.11 device is suspected of causing interference on the WLAN. You are not certain of the location or type of device. What is the best solution for locating this non- 802.11 device?

  A. Access point spectrum analyzer
  B. Laptop-based spectrum analyzer with an omni-directional antenna
  C. Laptop-based spectrum analyzer with an omni-directional antenna
  D. Laptop-based spectrum analyzer with a directional antenna
  D. Laptop-based spectrum analyzer with a directional antenna

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  Explanation/Reference:

  A laptop-based spectrum analyzer with a directional antenna is the best solution for locating a non-802.11 device that is suspected of causing interference on the WLAN. A spectrum analyzer is a device or a software application that can measure and display the frequency spectrum of electromagnetic signals in a given range. A spectrum analyzer can show the amplitude, frequency, bandwidth, modulation, and other characteristics of different signals in the spectrum, which can help identify their sources and types. A spectrum analyzer can also detect non-802.11 devices that may cause interference on the WLAN, such as microwave ovens, cordless phones, Bluetooth devices, or radar systems. A laptop-based spectrum analyzer is a software application that runs on a laptop computer and uses an external USB adapter as its RF interface. A laptop-based spectrum analyzer has the advantage of being portable, flexible, and cost-effective compared to a hardware- based spectrum analyzer. A directional antenna is an antenna that radiates or receives RF signals more strongly in one direction than in others. A directional antenna has a high gain and a narrow beamwidth, which means it can focus the RF energy in a specific direction and reduce the interference from other directions. A directional antenna can also increase the range and sensitivity of the RF signal detection. To locate a non-802.11 device that is causing interference on the WLAN, a laptop-based spectrum analyzer with a directional antenna can be used to perform a technique called RF hunting or triangulation. This technique involves pointing the directional antenna in different directions and observing the signal strength and characteristics of the interfering device on the spectrum analyzer. By moving around and changing the direction of the antenna, the location of the interfering device can be estimated based on where the signal strength is highest and most consistent. References: 1, Chapter 7, page 282; 2, Section 4.3

• Question 112:

  Which one of the following is not a factor considered when calculating the Link Budget for an outdoor point-to- point WLAN bridge link?

  A. Operating frequency
  B. MU-MIMO capabilities of the bridges
  C. Receive antenna gain
  D. Transmit power
  B. MU-MIMO capabilities of the bridges

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  Explanation/Reference:

  MU-MIMO capabilities of the bridges are not a factor considered when calculating the Link Budget for an outdoor point-to-point WLAN bridge link. The Link Budget is acalculation of the expected signal strength at the receiver based on various factors that affect the RF transmission. Some of these factors are operating frequency, transmit power, receive antenna gain, free space path loss, cable loss, connector loss, and environmental loss. MU-MIMO stands for Multi-User Multiple Input Multiple Output, which is a technology that allows multiple devices to communicate simultaneously using multiple spatial streams. MU-MIMO is not relevant for a point-to-point link, where there are only two devices involved. References: 1, Chapter 2, page 59; 2, Section 2.2

• Question 113:

  Which directional antenna types are commonly used by indoor Wi-Fi devices in a MIMO multiple spatial stream implementation?

  A. Dipole and yagi
  B. Grid and sector
  C. Patch and panel
  D. Dish and grid
  C. Patch and panel

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  Explanation/Reference:

  Patch and panel antennas are directional antenna types that are commonly used by indoor Wi-Fi devices in a MIMO multiple spatial stream implementation. These antennas have a flat rectangular shape and can be mounted on walls or ceilings to provide coverage in a specific direction. They have a moderate gain and a relatively wide beamwidth, making them suitable for multipath environments where signals can reflect off different surfaces and create multiple spatial streams. Patch and panel antennas can also support polarization diversity, which means they can transmit and receive both horizontally and vertically polarized waves, increasing the MIMO performance. References: 1, Chapter 2, page 72; 2, Section 2.4

• Question 114:

  You support a WLAN using dual-band 802.11ac three stream access points. All access points have both the 2.4 GHz and 5 GHz radios enabled and use 40 MHz channels in 5 GHz and 20 MHz channels in 2.4 GHz. A manager is concerned about the fact that each access point is connected using a 1 Gbps Ethernet link. He is concerned that the Ethernet link will not be able to handle the load from the wireless radios. What do you tell him?

  A. His concern is valid and the company should upgrade all Ethernet links to 10 Gbps immediately.
  B. His concern is valid and the company should immediately plan to run a second 1 Gbps Ethernet link to each AP.
  C. His concern is invalid because the AP will compress all data before transmitting it onto the Ethernet link.
  D. Due to 802.11 network operations and the dynamic rates used by devices on the network, the two radios will likely not exceed the 1 Gpbs Ethernet link.
  D. Due to 802.11 network operations and the dynamic rates used by devices on the network, the two radios will likely not exceed the 1 Gpbs Ethernet link.

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  Explanation/Reference:

  What you should tell him is that due to 802.11 network operations and the dynamic rates used by devices on the network, the two radios will likely not exceed the 1 Gbps Ethernet link. This is because the actual throughput of an 802.11 network is much lower than the theoretical data rates due to factors such as overhead, contention, interference, retransmissions, and environmental conditions. Moreover, the data rates used by devices on the network vary depending on their distance, signal quality, capabilities, and configuration. Therefore, it is unlikely that both radios of the AP will simultaneously use the maximum data rates and saturate the 1 Gbps Ethernet link. Upgrading to a 10 Gbps Ethernet link or running a second 1 Gbps Ethernet link may be unnecessary and costly. Compressing all data before transmitting it onto the Ethernet link may introduce additional overhead and latency. References: [CWNP CertifiedWireless Network Administrator Official Study Guide: ExamCWNA-109], page 227; [CWNA: Certified Wireless Network Administrator Official Study Guide: ExamCWNA-109], page 217.

• Question 115:

  You are deploying a WLAN monitoring solution that utilizes distributed sensor devices. Where should sensors be deployed for best results? Choose the single best answer.

  A. In switching closets
  B. Every 5 meters and alongside each AP
  C. In critical areas where WLAN performance must be high
  D. Above the plenum on each floor
  C. In critical areas where WLAN performance must be high

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  Explanation/Reference:

  Sensors should be deployed in critical areas where WLAN performance must be high for best results when using a WLAN monitoring solution that utilizes distributed sensor devices. A WLAN monitoring solution is a system that collects, analyzes, and reports on the status and performance of a WLAN. A WLAN monitoring solution can use different methods to gather data from the WLAN, such as embedded software agents, external hardware probes, or distributed sensor devices. Distributed sensor devices are dedicated devices that are deployed throughout the WLAN coverage area to monitor the wireless traffic and environment. Distributed sensor devices can perform various functions, such as scanning the spectrum, capturing wireless frames, measuring signal quality, detecting rogue access points, testing connectivity, and generating alerts. Distributed sensor devices can provide more accurate and comprehensive data than other methods, but they also require more planning and deployment costs. Therefore, it is important to deploy sensors strategically in critical areas where WLAN performance must be high, such as high-density zones, high-priority applications, or high-security locations. By deploying sensors in critical areas, the WLAN monitoring solution can ensure optimal WLAN performance and reliability in those areas and identify and resolve any issues or problems that may arise. The other options are not the best places to deploy sensors for best results. Deploying sensors in switching closets is not effective because sensors need to be close to the wireless medium to monitor it properly. Deploying sensors every 5 meters and alongside each AP is not efficient because sensors may overlap or interfere with each other and cause unnecessary redundancy or complexity. Deploying sensors above the plenum oneach floor is not practical because sensors may not capture the wireless traffic and environment accurately due to attenuation or reflection from the ceiling materials or objects. References: CWNA-109 Study Guide, Chapter 14: Troubleshooting Wireless LANs, page 4831

• Question 116:

  You administer a WLAN that offers a guest SSID of GUESTNWORK. Users connect to the GUESTNWORK SSID, but report that they cannot browse the Internet. The devices simply report no Internet connection. What common problem causes this scenario?

  A. NTP issues
  B. Hardware issues
  C. IP routing issues
  D. Captive portal issues
  D. Captive portal issues

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  Explanation/Reference:

  A common problem that causes this scenario is captive portal issues. A captive portal is a web page that requires users to authenticate or accept terms and conditions before accessing the Internet through a WLAN. A captive portal is often used for guest networks to provide security and control over the network access. A captive portal works by intercepting the user's web requests and redirecting them to the portal page until the user completes the required action. However, sometimes the captive portal may not work properly due to various reasons, such as browser settings, firewall rules, DNS configuration, or network errors. This can prevent the user from browsing the Internet or seeing the portal page. To troubleshoot captive portal issues, you can try to use a different browser, clear the browser cache andcookies, disable any VPN or proxy settings, manually enter the portal URL, or contact the network administrator. NTP issues, hardware issues, or IP routing issues are not common problems that cause this scenario. References: [CWNP Certified Wireless Network Administrator Official Study Guide: ExamCWNA-109], page 343; [CWNA: Certified Wireless Network Administrator Official Study Guide: ExamCWNA-109], page 333.

• Question 117:

  The IEEE 802.11-2012 standard requires VHT capable devices to be backward compatible with devices using which other 802.11 physical layer specifications (PHYs)?

  A. OFDM
  B. HR/DSSS
  C. ERP-PBCC
  D. DSSS-OFDM
  A. OFDM

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  Explanation/Reference:

  OFDM (Orthogonal Frequency Division Multiplexing) is the physical layer specification (PHY) that VHT capable devices must be backward compatible with according to the IEEE 802.11-2012 standard. VHT (Very High Throughput) is aPHY and MAC enhancement that is defined in the IEEE 802.11ac amendment and is also known as Wi-Fi

  5. VHT operates only in the 5 GHz band and uses features such as wider channel bandwidths (up to 160 MHz), higher modulation schemes (up to 256-QAM), more spatial streams (up to eight), multi-user MIMO (MU-MIMO), beamforming, and VHT PHY and MAC enhancements. VHT can achieve data rates up to 6.9 Gbps. According to the IEEE 802.11-2012 standard, VHT capable devices must be backward compatible with devices using OFDM PHY, which is defined in the IEEE 802.11a amendment and is also used by IEEE 802.11g, IEEE 802.11n, and IEEE 802.11h amendments. OFDM operates in both the 2.4 GHz and 5 GHz bands and uses features such as subcarriers, symbols, guard intervals, and OFDM PHY and MAC enhancements. OFDM can achieve data rates up to 54 Mbps. Backward compatibility means that VHT capable devices can interoperate with OFDM devices on the same network by using common features and parameters that are supported by both PHYs. For example, VHT capable devices can use a channel bandwidth of 20 MHz, a modulation scheme of BPSK, QPSK, or 16-QAM, one spatial stream, no beamforming, and OFDM PHY and MAC headers when communicating with OFDM devices. Backward compatibility also means that VHT capable devices can fall back to OFDMmode when the signal quality or SNR is too low for VHT mode. References: 1, Chapter 3, page 123; 2, Section 3.2

• Question 118:

  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
  B. 802.1X/EAP

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  Explanation/Reference:

  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, EAP-PEAP,

  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: ExamCWNA-109], page 299; [CWNA: Certified Wireless Network Administrator Official Study Guide: ExamCWNA-109], page 289.

• Question 119:

  What terms accurately complete the following sentence?

  The IEEE 802.11-2016 standard specifies mandatory support of the _______________ cipher suite for Robust Security Network Associations, and optional use of the ________________ cipher suite, which is designed for use with pre-RSNA hardware and is deprecated.

  A. 802.1X/EAP, WEP
  B. CCMP, TKIP
  C. TLS, SSL
  D. RC5, RC4
  B. CCMP, TKIP

• Question 120:

  What is the most effective method for testing roaming in relation to 802.11 VoIP handsets?

  A. Use a spectrum analyzer to monitor RF activity during a VoIP call.
  B. Use a protocol analyzer to capture the traffic generated when a laptop roams.
  C. Place a call with the handset and move around the facility to test quality during roaming.
  D. Use the built-in roaming monitor built into all VoIP handsets.
  C. Place a call with the handset and move around the facility to test quality during roaming.

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  Explanation/Reference:

  The most effective method for testing roaming in relation to 802.11 VoIP handsets is to place a call with the handset and move around the facility to test quality duringroaming. This method allows you to evaluate the actual performance and user experience of VoIP calls over wireless networks, as well as identify any potential issues such as signal strength, interference, latency, jitter, packet loss, or handoff delays. A spectrum analyzer can only show you the RF activity during a VoIP call, but not how it affects the voice quality or roaming behavior. A protocol analyzer can capture the traffic generated when a laptop roams, but it cannot simulate the characteristics of a VoIP handset such as battery life, antenna design, codec support, or QoS features. A built-in roaming monitor is not a common feature in all VoIP handsets, and it may not provide accurate or comprehensive information about the roaming process. References: [CWNP Certified Wireless Network Administrator Official Study Guide: ExamCWNA-109], page 487; [Voice over Wireless LAN 4.1 Design Guide], page 6-19.