QUESTION: 57

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?

The AP is overloaded during the work day
The drivers in the laptop are corrupt
The laptop has a failing wireless adapter
The external hard drive is USB 3.0 and is causing a significant increase in the noise floor when in use

Answer(s): D

Explanation:

The likely cause of the problem is that the external hard drive is USB 3.0 and is causing a significant increase in the noise floor when in use. USB 3.0 devices are known to generate radio frequency interference (RFI) in the 2.4 GHz band due to their high data transfer rates and harmonics. This RFI can increase the noise floor and degrade the signal-to-noise ratio (SNR) of WLAN devices operating in the same band. This can result in lower data rates, reduced throughput, increased retransmissions, and poor performance. The problem may not occur outside of business hours or on the user's home network because of different usage patterns or environmental factors.

Reference:

[CWNP Certified Wireless Network Administrator Official Study Guide: Exam CWNA-109], page 527; [CWNA: Certified

Wireless Network Administrator Official Study Guide: Exam CWNA-109], page 497.

Reveal Solution Next Question

QUESTION: 58

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

WAN interface analysis results
Capacity analysis results
Application Layer protocol availability analysis results
Layer 4 protocol availability analysis results

Answer(s): B

Explanation:

In addition to coverage analysis results, what should be included in a post-deployment site survey report to ensure WLAN users experience acceptable performance is Capacity analysis results. Capacity analysis is a method of testing the ability of the WLAN to support the expected number and type of users, devices, and applications. Capacity analysis can help to determine the optimal number and placement of access points, the appropriate channel and power settings, the required QoS policies, and the expected throughput and latency levels. Capacity analysis results can help to verify that the WLAN meets the performance requirements and service level agreements (SLAs) of the organization.

Reference:

[CWNP Certified Wireless Network Administrator Official Study Guide: Exam CWNA-109], page 548; [CWNA: Certified Wireless Network Administrator Official Study Guide: Exam CWNA-109], page 518.

Reveal Solution Next Question

QUESTION: 59

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?

The clients are configured to use WPA and 5 GHz channels only support WPA2.
The client drivers are faulty and should be upgraded.
The antennas in the laptop have insufficient gain to detect the 5 GHz signals.
The access points are configured to disallow 5 GHz.

Answer(s): B

Explanation:

The client drivers are faulty and should be upgraded is the likely problem for the laptop that can see and connect to 2.4 GHz APs, but does not even see 5 GHz APs. The client drivers are the software components that enable the wireless adapter of the laptop to communicate with the operating system and the network. The client drivers are responsible for scanning the available wireless channels, detecting and connecting to the access points, negotiating the security and data rate parameters, and transmitting and receiving data frames. If the client drivers are faulty, outdated, or incompatible, they may cause various issues with the wireless performance and functionality, such as low data rates, poor signal strength, frequent disconnections, or inability to see or connect to certain access points or channels.
One of the possible causes of faulty client drivers is that they do not support or recognize some of the features or standards of the 802.11ac technology, such as wider channel bandwidths, higher modulation schemes, or DFS (Dynamic Frequency Selection) channels. This could explain why the laptop can see and connect to 2.4 GHz APs, but not 5 GHz APs, as 802.11ac operates only in the 5 GHz band and uses channels that are wider (up to 160 MHz) and higher (up to channel 165) than those used by previous standards. Moreover, some of the 5 GHz channels are subject to DFS rules, which require the access points and client stations to monitor and avoid using channels that are occupied by radar systems or other primary users. If the client drivers do not support or comply with

DFS rules, they may not be able to see or connect to access points that use DFS channels. To solve this problem, the client drivers should be upgraded to the latest version that supports and is compatible with 802.11ac features and standards. This can be done by downloading and installing the updated driver software from the manufacturer's website or using a device manager tool. Upgrading the client drivers may also improve other aspects of wireless performance and functionality, such as data rates, signal strength, security, and stability.

Reference:

1, Chapter 12, page 493; 2, Section 8.1

Reveal Solution Next Question

QUESTION: 60

A client complains of low data rates on his computer.
When you evaluate the situation, you see that the signal strength is -84 dBm and the noise floor is -96 dBm. The client is an 802.11ac client and connects to an 802.11ac AP. Both the client and AP are 2x2:2 devices.
What is the likely cause of the low data rate issue?

Weak signal strength
CAT5e cabling run to the AP
Too few spatial streams
Lack of support for 802.11n

Answer(s): A

Explanation:

Weak signal strength is the likely cause of the low data rate issue for the client that has a signal strength of -84 dBm and a noise floor of -96 dBm. The client is an 802.11ac client and connects to an 802.11ac AP. Both the client and AP are 2x2:2 devices. Signal strength is the measure of how strong the RF signal is at the receiver. Signal strength can affect the reliability and performance of the wireless connection, as well as the data rate and throughput of the traffic. The higher the signal strength, the better the signal quality and the higher the data rate. The lower the signal strength, the worse the signal quality and the lower the data rate.
The data rate of an 802.11ac connection depends on several factors, such as channel bandwidth, modulation and coding scheme (MCS), spatial streams, guard interval, and beamforming. However, these factors are also influenced by the signal strength, as they require a certain signal-to-noise ratio (SNR) to operate properly. SNR is the ratio of the signal strength to the noise floor, which is the measure of the background noise or interference in the RF environment. The higher the SNR, the more robust and efficient the communication. The lower the SNR, the more prone and vulnerable to errors and retries.
According to the CWNA Official Study Guide , Table 3.7, page 112, an 802.11ac connection with a channel bandwidth of 80 MHz, an MCS of 9, two spatial streams, a short guard interval, and no beamforming can achieve a maximum data rate of 867 Mbps. However, this data rate requires a minimum SNR of 30 dB to maintain a sufficient signal quality. If the signal strength is -84 dBm and the noise floor is -96 dBm, then the SNR is only 12 dB (-84 dBm - (-96 dBm) = 12 dB), which is far below the required SNR for this data rate. Therefore, the data rate will drop significantly to match the lower SNR and signal quality.
To solve this problem, the signal strength should be increased to improve the SNR and data rate. This can be done by adjusting the output power or channel assignment of the AP or client, relocating or reorienting some APs or antennas to reduce attenuation or interference, updating or replacing some faulty or outdated hardware or software components, etc.

Reference:

, Chapter 3, page 112; , Section

3.2

Reveal Solution Next Question

Free CWNA-109 Exam Braindumps (page: 15)

QUESTION: 57

Explanation:

Reference:

QUESTION: 58

Explanation:

Reference:

QUESTION: 59

Explanation:

Reference:

QUESTION: 60

Explanation:

Reference: