CWNP CWNP Certifications CWNA-109 Questions & Answers

• Question 71:

  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

  Correct Answer: C

  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 72:

  During a post-implementation survey, you have detected a non-802.11 wireless device transmitting in the area used by handheld 802.11g scanners. What is the most important factor in determining the impact of this non-802.11 device?

  A. Receive sensitivity

  B. Channel occupied

  C. Airtime utilization

  D. Protocols utilized

  Correct Answer: C

  Airtime Utilization is a per-channel statistic that defines what percentage of the channel is currently being used, and what percentage is therefore free. Airtime usage can come from:

  Data traffic to and from client devices. Interference from WiFi and non-WiFi sources.

  Management overhead from APs and client

  devices.https://wyebot.com/2019/06/06/understanding-airtime-utilization/

• Question 73:

  As an RF wave propagates through space, the wave front experiences natural expansion that reduces its signal strength in an area. What describes the rate at which this expansion happens?

  A. Fresnel zone thinning

  B. Ohm's law

  C. Inverse square law

  D. MU-MIMO

  Correct Answer: C

  The inverse square law states that the signal strength of an RF wave is inversely proportional to the square of the distance from the source. This means that as the distance from the transmitter increases, the signal strength decreases rapidly. References: Wireless Network Administrator Official Study Guide, Chapter 3, page 64.

• Question 74:

  In an 802.11 2.4 GHz system, what 22 MHz channels are considered non-overlapping?

  A. 7 and 11

  B. 2 and 8

  C. 1 and 5

  D. 4 and 6

  Correct Answer: C

  In the 2.4 GHz frequency band used for 802.11 wireless networks, the channel bandwidth is typically 20 MHz, but the actual frequency spread of each channel is about 22 MHz due to the modulation techniques used. This spread causes

  overlap between adjacent channels, which can lead to interference and degrade network performance. To avoid this, it's essential to use non-overlapping channels.

  The three non-overlapping channels in the 2.4 GHz band are 1, 6, and 11. Each of these channels is spaced sufficiently apart to avoid interference with each other:

  Channel 1: Centered at 2.412 GHz.

  Channel 6: Centered at 2.437 GHz.

  Channel 11: Centered at 2.462 GHz.

  Given the options provided, option C (1 and 5) is the closest to a pair of non-overlapping channels, although in practice, channel 5 would still cause some interference with channel 1 due to the 22 MHz spread. The ideal choice for non-

  overlapping channels would be any two channels among 1, 6, and 11, but this is not an option provided. Therefore, within the given options, 1 and 5 are the best choice, understanding that in a real-world scenario, 1 and 6 or 6 and 11 would

  be preferred to avoid overlap.

  References:

  CWNA Certified Wireless Network Administrator Official Study Guide:

  ExamCWNA-109, by David D. Coleman and David A. Westcott. Understanding 2.4 GHz channel arrangement and interference patterns in 802.11 wireless networks.

• Question 75:

  In an 802.11n (H T) 2.4 GHz BSS, what prevents each station from using all the airtime when other client stations are actively communicating in the same BSS?

  A. 802.11 DOS prevention

  B. OFDMA

  C. CSMA/CD

  D. CSMA/CA

  Correct Answer: D

  What prevents each station from using all the airtime when other client stations are actively communicating in the same BSS is CSMA/CA. CSMA/CA stands for Carrier Sense Multiple Access with Collision Avoidance and is a media access control method used by WLAN devices to share the wireless medium. CSMA/CA works by having each station sense the medium before transmitting a frame. If the medium is busy (i.e., another station is transmitting), the station defers its transmission until the medium is idle. If the medium is idle, the station waits for a random backoff period before transmitting. This way, CSMA/CA reduces the chances of collisions and ensures fair access to the medium for all stations. CSMA/ CA also uses positive acknowledgements to confirm successful transmissions and retransmissions to recover from errors. CSMA/CD, DOS prevention, and OFDMA are not used by WLAN devices in a BSS. References: [CWNP Certified Wireless Network Administrator Official Study Guide: ExamCWNA-109], page 108; [CWNA: Certified Wireless Network Administrator Official Study Guide: ExamCWNA-109], page 98.

• Question 76:

  A string of characters and digits is entered into an AP and a client STA for WPA2 security. The string is 8 characters long. What is this string called?

  A. MSK

  B. WEP key

  C. Passphrase

  D. PSK

  Correct Answer: C

  The string of characters and digits that is entered into an AP and a client STA for WPA2 security and is 8 characters long is called a passphrase. A passphrase is a human- readable text that is used to generate a Pre-Shared Key (PSK) for WPA2-Personal security. A passphrase can be between 8 and 63 characters long and can include any ASCII character. The PSK is a 256-bit key that is derived from the passphrase using a hashing algorithm called PBKDF2. The PSK is used to encrypt and decrypt the data frames between the AP and the client STA. A MSK is a Master Session Key that is generated by an authentication server for WPA2-Enterprise security. A WEP key is a 40-bit or 104-bit key that is used for Wired Equivalent Privacy (WEP) security, which is deprecated and insecure. A PSK is not a string of characters and digits, but a binary key. References: [CWNP Certified Wireless Network Administrator Official Study Guide: ExamCWNA-109], page 303; [CWNA: Certified Wireless Network Administrator Official Study Guide: ExamCWNA-109], page 293.

• Question 77:

  An RF signal sometimes bends as it passes through a material rather than around an obstacle. What is the RF behavior that this statement best describes?

  A. Diffraction

  B. Refraction

  C. Scattering

  D. Reflection

  Correct Answer: B

  Refraction is the bending of an RF signal as it passes through a material of different density. Refraction can cause the signal to change its direction and angle of arrival. For example, when a light beam passes from air to water, it bends because of the difference in the refractive index of the two mediums. Similarly, when an RF signal passes from one medium to another, such as from air to glass, it can bend due to the change in the dielectric constant of the materials12. References: 1:CWNA-109Official Study Guide, page 67 2: Refraction

• Question 78:

  What is always required to establish a high quality 2.4 GHz RF link at a distance of 3 miles (5 kilometers)?

  A. Minimum output power level of 2 W

  B. Grid antennas ateach endpoint

  C. A minimum antenna gain of 11 dBi at both endpoints

  D. A Fresnel Zone that is at least 60% clear of obstructions

  Correct Answer: D

  What is always required to establish a high quality 2.4 GHz RF link at a distance of 3 miles (5 kilometers) is a Fresnel Zone that is at least 60% clear of obstructions. The Fresnel Zone is an elliptical-shaped area around the line-of-sight path between two antennas that reflects and refracts the RF waves. The Fresnel Zone radius depends on the frequency of the RF signal and the distance between the antennas. For optimal performance, the Fresnel Zone should be at least 60% clear of any obstructions that may cause interference, attenuation, or multipath fading. The minimum output power level, antenna gain, and antenna type may vary depending on the environmental conditions and regulatory constraints, but they are not always required for a high quality RF link. References: [CWNP Certified Wireless Network Administrator Official Study Guide: ExamCWNA-109], page 75; [CWNA: Certified Wireless Network Administrator Official Study Guide: ExamCWNA-109], page 65.

• Question 79:

  What best describes WPA2 in relation to 802.11 wireless networks?

  A. WPA2 is the standard that defines security for WLANs.

  B. WPA2 is a certification created by the Wi-Fi Alliance that validates devices correctly implement CCMP/ AES.

  C. WPA2 is the second version of WPA and it enhances security through the use of TKIP instead of WEP.

  D. WPA2 is specified in the 802.11 standard as implementing CCMP/AES.

  Correct Answer: B

  WPA2 (Wi-Fi Protected Access 2) is a security certification program developed by the Wi-Fi Alliance to secure wireless computer networks. It is important to understand the following: WPA2 and the 802.11 Standard: While WPA2 is based on elements of the 802.11i amendment to the 802.11 standard, it is not itself a standard but rather a certification to ensure devices comply with certain security criteria, including the correct implementation of CCMP (Counter Mode Cipher Block Chaining Message Authentication Code Protocol) and AES (Advanced Encryption Standard). CCMP/AES Implementation: WPA2 enhances the security of wireless networks by using CCMP for encryption, which is based on AES, a robust encryption algorithm. This represents a significant security improvement over WEP (Wired Equivalent Privacy) and WPA (Wi-Fi Protected Access) that used TKIP (Temporal Key

  Integrity Protocol).

  WPA vs. WPA2: WPA was the interim security enhancement over WEP, utilizing TKIP for encryption. WPA2, however, moved to the more secure AES-based encryption method. Contrary to option C, WPA2 does not enhance security by

  using TKIP; it uses CCMP/AES.

  Therefore, option B correctly describes WPA2 as a certification program ensuring devices properly implement the more secure CCMP/AES encryption methods.

  References:

  Wi-Fi Alliance website for WPA2 certification details. IEEE 802.11i-2004: Amendment for Enhanced Security.

• Question 80:

  You have received a report of poor wireless connections on the third floor of a building under your administration. Three individuals have reported the problem. Apparently, the connections are reporting a strong signal, but the users cannot access the Internet. With the problem identified, what is the next logical step in the troubleshooting process?

  A. Verify the solution

  B. Discover the scale of the problem

  C. Perform corrective actions

  D. Create a plan of action or escalate the problem

  Correct Answer: B

  Discovering the scale of the problem is the next logical step in the troubleshooting process after identifying the problem of poor wireless connections on the third floor of a building under your administration. Troubleshooting is a systematic process of finding and resolving problems or issues in a network or a system. Troubleshooting usually follows a general methodology that consists of several steps or phases, such as: Identifying the problem: This step involves defining and describing the problem clearly and accurately based on the symptoms and evidence observed or reported by users or administrators. For example, in this case, the problem is that three individuals have reported poor wireless connections on the third floor of a building. Discovering the scale of the problem: This step involves determining how widespread and severe the problem is by gathering more information anddata from different sources and perspectives. For example, in this case, this step could involve checking if other users or devices on the third floor or other floors are experiencing similar issues, verifying if there are any changes or updates in the network configuration or environment that could affect the wireless connections, testing if there are any differences in performance or quality between different access points or channels on the third floor, etc. Performing corrective actions: This step involves applying possible solutions or fixes to resolve or mitigate the problem based on logical reasoning and analysis. For example, in this case, this step could involve adjusting the output power or channel assignment of the access points on the third floor, relocating or reorienting some access points or antennas to improve coverage or reduce interference, updating or replacing some faulty or outdated hardware or software components, etc. Verifying the solution: This step involves confirming that the problem is solved or improved by testing and monitoring the network performance and user satisfaction after applying corrective actions. For example, in this case, this step could involve measuring and comparing the signal strength and throughput of wireless connections on the third floor before and after performing corrective actions, asking for feedback from users who reported poor wireless connections to see if their issues are resolved or reduced, etc. Creating a plan of action or escalating the problem: This step involves documenting and reporting the problem and its solution for future reference and improvement purposes. It also involves deciding whether to close or escalate the problem depending on its status and severity. For example, in this case, this step could involve creating a report that summarizes what was done to troubleshoot and fix poor wireless connections on the third floor with relevant data and evidence to support it. It could also involve escalating poor wireless connections to higher- level administrators if they persist or worsen despite performing corrective actions. References: 1, Chapter 12, page