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

A.
7 and 11
A.
7 and 11
Answers
B.
2 and 8
B.
2 and 8
Answers
C.
1 and 5
C.
1 and 5
Answers
D.
4 and 6
D.
4 and 6
Answers
Suggested answer: C

Explanation:

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.

CWNA Certified Wireless Network Administrator Official Study Guide: Exam CWNA-109, by David D. Coleman and David A. Westcott.

Understanding 2.4 GHz channel arrangement and interference patterns in 802.11 wireless networks.

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
A.
Verify the solution
Answers
B.
Discover the scale of the problem
B.
Discover the scale of the problem
Answers
C.
Perform corrective actions
C.
Perform corrective actions
Answers
D.
Create a plan of action or escalate the problem
D.
Create a plan of action or escalate the problem
Answers
Suggested answer: B

Explanation:

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 and data 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.

What is the final step in an effective troubleshooting process?

A.
Disable the WLAN
A.
Disable the WLAN
Answers
B.
Verify the solution
B.
Verify the solution
Answers
C.
Notify the users of problem resolution
C.
Notify the users of problem resolution
Answers
D.
Document the results
D.
Document the results
Answers
Suggested answer: D

Explanation:

The final step in an effective troubleshooting process is todocument the results. Documentation is essential for keeping track of the problem history, the actions taken, the solutions implemented, and the outcomes achieved. Documentation can also help to prevent future problems, improve best practices, and provide feedback for improvement. Documentation should include relevant information such as problem description, symptoms, root cause analysis, resolution steps, verification methods, and lessons learned.Reference:[CWNP Certified Wireless Network Administrator Official Study Guide: Exam CWNA-109], page 513; [CWNA: Certified Wireless Network Administrator Official Study Guide: Exam CWNA-109], page 483.

You are troubleshooting a problem with interference from a non-802.11 device. Given that the device is not a WLAN device, you cannot use a protocol analyzer and have chosen to use a spectrum analyzer. You want to view the signal from the interfering device over time to see the activity that is generating.

What common spectrum analyzer view should you use for this analysis?

A.
APs
A.
APs
Answers
B.
Waterfall/Spectrogram
B.
Waterfall/Spectrogram
Answers
C.
Real-time FFT
C.
Real-time FFT
Answers
D.
Clients
D.
Clients
Answers
Suggested answer: B

Explanation:

The common spectrum analyzer view that you should use for this analysis is theWaterfall/Spectrogramview. The Waterfall/Spectrogram view shows the signal from the interfering device over time on a three-dimensional graph. The x-axis represents frequency, the y-axis represents time, and the z-axis represents amplitude or power. The color of each pixel indicates the signal strength at a given frequency and time. The Waterfall/Spectrogram view can help you identify the characteristics of the interference source, such as its frequency range, duty cycle, modulation type, and pattern.Reference:[CWNP Certified Wireless Network Administrator Official Study Guide: Exam CWNA-109], page 524; [CWNA: Certified Wireless Network Administrator Official Study Guide: Exam CWNA-109], page 494.

Your manager asked you to locate a solution that allows for centralized monitoring of WLAN performance over time. He wants a single pane of glass for administration and monitoring of the solution. What do you recommend?

A.
Laptop-based spectrum analyzers
A.
Laptop-based spectrum analyzers
Answers
B.
AP-based spectrum analysis
B.
AP-based spectrum analysis
Answers
C.
Overlay WLAN monitoring solution
C.
Overlay WLAN monitoring solution
Answers
D.
Laptop-based protocol analyzers
D.
Laptop-based protocol analyzers
Answers
Suggested answer: C

Explanation:

The solution that you recommend is anOverlay WLAN monitoring solution. An Overlay WLAN monitoring solution is a system that uses dedicated sensors or probes to monitor the WLAN performance over time. The sensors are deployed throughout the WLAN coverage area and collect data on various metrics such as signal strength, noise level, channel utilization, interference, throughput, latency, packet loss, and QoS. The sensors send the data to a centralized server or appliance that analyzes the data and provides a single pane of glass for administration and monitoring of the solution. An Overlay WLAN monitoring solution can help to detect and troubleshoot WLAN issues, optimize WLAN performance, and generate reports and alerts.Reference:[CWNP Certified Wireless Network Administrator Official Study Guide: Exam CWNA-109], page 538; [CWNA: Certified Wireless Network Administrator Official Study Guide: Exam CWNA-109], page 508.

You were previously onsite at XYZ's facility to conduct a pre-deployment RF site survey. The WLAN has been deployed according to your recommendations and you are onsite again to perform a post-deployment validation survey.

When performing this type of post-deployment RF site survey voice over Wi-Fi, what is an action that must be performed?

A.
Spectrum analysis to locate and identify RF interference sources.
A.
Spectrum analysis to locate and identify RF interference sources.
Answers
B.
Frequency-band hopping analysis to detect improper RF channel implementations.
B.
Frequency-band hopping analysis to detect improper RF channel implementations.
Answers
C.
Application analysis with an active phone call on an VoWiFi handset.
C.
Application analysis with an active phone call on an VoWiFi handset.
Answers
D.
Protocol analysis to discover channel use on neighboring APs.
D.
Protocol analysis to discover channel use on neighboring APs.
Answers
Suggested answer: C

Explanation:

When performing a post-deployment validation survey for voice over Wi-Fi (VoWiFi), an action that must be performed isApplication analysis with an active phone call on a VoWiFi handset. Application analysis is a method of testing the performance of a specific application over the WLAN by measuring parameters such as throughput, latency, jitter, packet loss, MOS score, and R-value. Application analysis with an active phone call on a VoWiFi handset can help to evaluate the quality of service (QoS) and user experience of VoWiFi calls over the WLAN. It can also help to identify any issues or bottlenecks that may affect VoWiFi calls such as interference, roaming delays, or insufficient coverage.Reference:[CWNP Certified Wireless Network Administrator Official Study Guide: Exam CWNA-109], page 549; [CWNA: Certified Wireless Network Administrator Official Study Guide: Exam CWNA-109], page 519.

When a STA has authenticated to an AP (AP-1), but still maintains a connection with another AP (AP-2), what is the state of the STA on AP-1?

A.
Transitional
A.
Transitional
Answers
B.
Unauthenticated and Unassociated
B.
Unauthenticated and Unassociated
Answers
C.
Authenticated and Unassociated
C.
Authenticated and Unassociated
Answers
D.
Authenticated and Associated
D.
Authenticated and Associated
Answers
Suggested answer: C

Explanation:

Authenticated and Unassociated.According to one of the web search results1, a STA can be authenticated to multiple APs, but it can only be associated to one AP at a time.Association is the process of establishing a logical link between the STA and the AP, which allows the STA to send and receive data frames through the AP2. Therefore, when a STA has authenticated to an AP-1, but still maintains a connection with another AP-2, it means that the STA is authenticated to both APs, but only associated to AP-2. The state of the STA on AP-1 is authenticated and unassociated, which means that the STA can switch to AP-1 without repeating the authentication process, but it cannot send or receive data frames through AP-1 until it becomes associated.

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
A.
MSK
Answers
B.
WEP key
B.
WEP key
Answers
C.
Passphrase
C.
Passphrase
Answers
D.
PSK
D.
PSK
Answers
Suggested answer: C

Explanation:

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 apassphrase. 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.Reference:[CWNP Certified Wireless Network Administrator Official Study Guide: Exam CWNA-109], page 303; [CWNA: Certified Wireless Network Administrator Official Study Guide: Exam CWNA-109], page 293.

When considering data rates available in HT and VHT PHY devices, in addition to the modulation, coding, channel width, and spatial streams, what impacts the data rate according to the MCS tables?

A.
Frequency band in use
A.
Frequency band in use
Answers
B.
client drivers
B.
client drivers
Answers
C.
guard interval
C.
guard interval
Answers
D.
Antenna Height
D.
Antenna Height
Answers
Suggested answer: C

Explanation:

The guard interval is a short period of time inserted between the symbols of an OFDM signal to prevent inter-symbol interference and improve the robustness of the transmission1. The guard interval can have different values depending on the 802.11 standard and the configuration of the device.For example, 802.11n supports two guard intervals: 800 ns (normal) and 400 ns (short)2.802.11ac supports the same guard intervals as 802.11n, plus an optional 200 ns guard interval for 80 MHz and 160 MHz channels3.802.11ax supports three guard intervals: 800 ns, 1600 ns, and 3200 ns4.

The guard interval affects the data rate because it determines the duration of each symbol. A shorter guard interval means more symbols can be transmitted in a given time, resulting in a higher data rate. However, a shorter guard interval also means less protection against inter-symbol interference, which may degrade the signal quality and increase the error rate. Therefore, there is a trade-off between data rate and reliability when choosing the guard interval.

The MCS tables for HT and VHT PHY devices show the data rates for different combinations of modulation, coding, channel width, spatial streams, and guard intervals.For example, for a VHT device using MCS 9 with QAM-256 modulation, 5/6 coding rate, 80 MHz channel width, and one spatial stream, the data rate is 433.3 Mbps with a normal guard interval (800 ns) and 486.7 Mbps with a short guard interval (400 ns)2. Therefore, the guard interval impacts the data rate according to the MCS tables.

An RF signal sometimes bends as it passes through some material other than free space. What is the term that describes this behavior?

A.
Refraction
A.
Refraction
Answers
B.
Warping
B.
Warping
Answers
C.
Scattering
C.
Scattering
Answers
D.
Reflection
D.
Reflection
Answers
Suggested answer: A

Explanation:

Refraction is the bending of an RF signal as it passes through a medium with a different density than free space. This can cause the signal to change its direction and speed, which can affect the accuracy and reliability of wireless communication.Refraction is influenced by factors such as temperature, humidity, and atmospheric pressure12.Reference:CWNA-109 Study Guide, Chapter 2: Radio Frequency Fundamentals, page 72;CWNA-109 Study Guide, Chapter 2: Radio Frequency Fundamentals, page 67.

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