CWNP CWNP Certifications CWNA-109 Questions & Answers

• Question 11:

  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.

  B. Frequency-band hopping analysis to detect improper RF channel implementations.

  C. Application analysis with an active phone call on an VoWiFi handset.

  D. Protocol analysis to discover channel use on neighboring APs.

  Correct Answer: C

  When performing a post-deployment validation survey for voice over Wi-Fi (VoWiFi), an action that must be performed is Application 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. References: [CWNP Certified Wireless Network Administrator Official Study Guide: ExamCWNA-109], page 549; [CWNA: Certified Wireless Network Administrator Official Study Guide: ExamCWNA-109], page 519.

• Question 12:

  Which unit of measurement, as formally defined, is an absolute unit that is used to quantify received signal power levels on a logarithmic scale?

  A. SNI

  B. VSWR

  C. dBm

  D. dBi

  Correct Answer: C

  The unit of measurement that is an absolute unit and is used to quantify received signal power levels on a logarithmic scale is dBm. dBm stands for decibel-milliwatt and represents the power level relative to 1 milliwatt (mW). dBm is an absolute unit because it has a fixed reference point and does not depend on the input power level. dBm is used to measure the received signal power levels on a logarithmic scale because it can express large variations in power levels with small numbers and make calculations easier. For example, a 10 dB increase in power level means a 10-fold increase in power, and a 20 dB increase means a 100-fold increase in power. References: [CWNP Certified Wireless Network Administrator Official Study Guide: ExamCWNA-109], page 66; [CWNA: Certified Wireless Network Administrator Official Study Guide: ExamCWNA-109], page 56.

• Question 13:

  An 802.11 WLAN transmitter that emits a 50 mW signal is connected to a cable with 3 dB of loss. The cable is connected to an antenna with 16 dBi of gain. What is the power level at the Intentional Radiator?

  A. 25 mW

  B. 250 mW

  C. 500 mW

  D. 1000 mW

  Correct Answer: B

  The power level at the Intentional Radiator (IR) is 250 mW. The IR is the point where the RF signal leaves the transmitter and enters the antenna system. To calculate the power level at the IR, we need to consider the output power level of

  the transmitter, the loss of the cable, and the gain of the antenna. The formula is:

  Power level at IR (dBm) = Output power level (dBm) - Cable loss (dB) + Antenna gain (dBi) We can convert the output power level of 50 mW to dBm by using the formula:

  Power level (dBm) = 10 * log10(Power level (mW))

  Therefore, 50 mW = 10 * log10(50) = 16.99 dBm

  We can plug in the values into the formula:

  Power level at IR (dBm) = 16.99 - 3 + 16 = 29.99 dBm We can convert the power level at IR from dBm to mW by using the inverse formula:

  Power level (mW) = 10^(Power level (dBm) / 10)

  Therefore, 29.99 dBm = 10^(29.99 / 10) = 999.96 mW However, since we need to round off the answer to the nearest integer value, we get:

  Power level at IR (mW) = 1000 mW

  References: [CWNP Certified Wireless Network Administrator Official Study Guide:

  ExamCWNA-109], page 67; [CWNA: Certified Wireless Network Administrator Official Study Guide: ExamCWNA-109], page 57.

• Question 14:

  What statement about 802.11 WLAN bridges is true?

  A. WLAN bridges only work in the 2.4 GHz frequency band and they support only SISO communications

  B. WLAN bridges must use a channel with acceptable SNR at both transceivers to maintain the desired data rate bi-directionally

  C. WLAN bridges may support MIMO communications, but only if used in the 5 GHz frequency band

  D. WLAN bridges must be implemented such that no interference occurs on the channel anywhere between the two endpoints used to establish the bridge

  Correct Answer: B

  WLAN bridges must use a channel with acceptable SNR at both transceivers to maintain the desired data rate bi-directionally. A WLAN bridge is a device that connects two or more networks using the 802.11 protocol. A WLAN bridge must have a clear and strong signal between the two endpoints to ensure reliable and fast data transmission. The signal-to- noise ratio (SNR) is a measure of the quality of the signal, which depends on the distance, interference, obstacles, and antenna gain between the transceivers. A higher SNR means a better signal quality and a higher data rate. A lower SNR means a worse signal quality and a lower data rate. Therefore, a WLAN bridge must use a channel with acceptable SNR at both transceivers to maintain the desired data rate bi-directionally1.

• Question 15:

  You are using a site survey tool for post-implementation validation. You have installed the appropriate adapter driver and imported a floor plan. Now, you want to take the next step in proper tool use. What must you do before gathering survey data after the floor plan is imported?

  A. Calibrate the floor plan

  B. Install WinPCAP

  C. Nothing, you can simply start capturing signal readings

  D. Install iPerf

  Correct Answer: A

  Calibrating the floor plan is what you must do before gathering survey data after the floor plan is imported when using a site survey tool for post-implementation validation. A site survey tool is a software application that can run on a laptop, tablet, smartphone, or other device that has a Wi-Fi adapter and a GPS receiver. A site survey tool can scan the wireless environment and collect information about the detected access points and client stations, such as their SSID, BSSID, channel, signal strength, security, and data rate. A site survey tool can also measure and display various metrics of network performance, such as throughput, jitter, packet loss, delay, and SNR. A site survey tool can also use a floor plan to visualize the wirelesscoverage and quality in different locations on a map. A floor plan is an image file that shows the layout and dimensions of a building or an area where the WLAN is deployed. A floor plan can be imported from various sources, such as a CAD file, a PDF file, an image file, or a Google Maps screenshot. After importing a floor plan into a site survey tool, it is necessary to calibrate the floor plan before gathering survey data. Calibrating the floor plan means adjusting the scale and orientation of the floor plan to match the actual size and direction of the area. Calibrating the floor plan can be done by using a reference point or a reference line that has a known distance or angle in the real world. Calibrating the floor plan ensures that the survey data is accurate and consistent with the physical environment. References: 1, Chapter 7, page 290; 2, Section 4.3

• Question 16:

  You are deploying a WLAN with the access points configured for 10 mW of output power on the 2.4 GHz radios and 20 mW of output power on the 5GHz radios. Some semi- directional antennas are also in use. What kind of deployment is described?

  A. SOHO

  B. Residential

  C. High density

  D. Standard office

  Correct Answer: A

  A high-density deployment is a wireless network that is designed to support a large number of users and devices in a relatively small area. This type of deployment is often used in enterprise environments, such as offices, schools, and

  hospitals. The use of semi-directional antennas in the deployment described in the question is a good indication that it is a high-density deployment. Semi-directional antennas can be used to focus the signal from an access point in a specific

  direction. This can help to reduce interference and improve performance in high-density environments. The other answer choices are less likely to be correct for the following reasons:

  SOHO (small office/home office) deployments are typically smaller and less complex than high-density deployments.

  Residential deployments are typically even smaller and less complex than SOHO deployments.

  Standard office deployments may be high-density, but they may also be lower- density.

  It is important to note that the type of deployment is not determined solely by the output power of the access points. However, the use of 10 mW of output power on the 2.4 GHz radios and 20 mW of output power on the 5GHz radios is also

  consistent with a high- density deployment.

  Here are some additional tips for deploying a high-density wireless network:

  Use a site survey to determine the optimal placement of access points. Configure the access points to use non-overlapping channels. Use semi-directional or directional antennas to focus the signal and reduce interference.

  Implement a wireless intrusion prevention system (WIPS) to detect and mitigate rogue access points and other security threats.

• Question 17:

  What factor is likely to cause the least impact on the application layer throughput of an 802.11n client station in a 2.4 GHz HT BSS?

  A. Increasing or decreasing the number of spatial streams in use by the client station and AP

  B. Implementing Fast BSS Transition (FT) for roaming

  C. Implementation of several other clients in the same BSS using 802.11g radios

  D. RF interference from more than 10 nearby Bluetooth transmitters

  Correct Answer: B

  Implementing Fast BSS Transition (FT) for roaming is likely to cause the least impact on the application layer throughput of an 802.11n client station in a 2.4 GHz HT BSS. FT is a feature that allows a client station to quickly switch from one AP to another within the same ESS (Extended Service Set) without having to re-authenticate and re- associate with each AP. This reduces the latency and packet loss that may occur during roaming, thus improving the user experience and maintaining the application layer throughput. FT is defined in the IEEE 802.11r amendment and is also known as Fast Roaming or Fast Secure Roaming. References: , Chapter 9, page 367; , Section 6.3

• Question 18:

  Which one of the following channels can be used for VHT transmissions according to the 802.11 specification?

  A. 6

  B. 144

  C. 1

  D. 11

  Correct Answer: B

  The channel that can be used for VHT transmissions according to the 802.11 specification is channel 144. VHT stands for Very High Throughput and is the PHY layer specification for 802.11ac devices. VHT transmissions can use channel bandwidths of 20 MHz, 40 MHz, 80 MHz, or 160 MHz in the 5 GHz band. Channel 144 is one of the channels in the 5 GHz band that can support VHT transmissions with any of these bandwidths. Channel 6, channel 1, and channel 11 are channels in the 2.4 GHz band that cannot support VHT transmissions, as they are only compatible with legacy (802.11b/g/n), HT (802.11n), or ERP (802.11g) transmissions with up to 20 MHz bandwidth. References: [CWNP Certified Wireless Network Administrator Official Study Guide: ExamCWNA-109], page 214; [CWNA: Certified Wireless Network Administrator Official Study Guide: ExamCWNA-109], page 204.

• Question 19:

  Lynne runs a small hotel, and as a value added service for his customers he has implemented a Wi-Fi hot-spot. Lynne has read news articles about how hackers wait at hot- spots trying to take advantage of unsuspecting users. He wants to avoid this problem at his hotel.

  What is an efficient and practical step that Lynne can take to decrease the likelihood of active attacks on his customers' wireless computers?

  A. Enable station-to-station traffic blocking by the access points in the hotel.

  B. Implement Network Access Control (NAC) and require antivirus and firewall software along with OS patches.

  C. Implement an SSL VPN in the WLAN controller that initiates after HTTPS login.

  D. Require EAP-FAST authentication and provide customers with a username/password on their receipt.

  Correct Answer: A

  In a public Wi-Fi hotspot, like the one Lynne runs in his hotel, ensuring customer security against active attacks is crucial. Active attacks involve unauthorized access, eavesdropping, or manipulation of the network traffic. To mitigate such

  threats, an effective and practical step is:

  Station-to-Station Traffic Blocking: Also known as client isolation, this feature prevents direct communication between devices connected to the Wi-Fi network. By enabling this on the access points, Lynne can significantly decrease the

  likelihood of active attacks like man-in-the-middle (MITM) attacks, where an attacker intercepts and possibly alters the communication between two parties. The other options, while beneficial for network security, might not be as

  straightforward or practical for Lynne's situation:

  Network Access Control (NAC)requires a more complex infrastructure and management, which might not be ideal for a small hotel setup. Implementing an SSL VPNadds an extra layer of security but might complicate the login process for

  users, potentially affecting the user experience. Requiring EAP-FAST authenticationprovides secure authentication but may not be feasible for transient customers who expect quick and easy network access. Therefore, enabling station-tostation traffic blocking is a practical and efficient measure that Lynne can implement to enhance customer security on the Wi-Fi network.

  References:

  CWNA Certified Wireless Network Administrator Official Study Guide:

  ExamCWNA-109, by David D. Coleman and David A. Westcott. Best practices for securing a wireless network in a public hotspot environment.

• Question 20:

  What 802.11 PHY uses available space in very low frequency ranges that is not in use at the time by broadcast video signals?

  A. DMG

  B. SIG

  C. DSSS

  D. TVHT

  Correct Answer: D

  TVHT stands for Television Very High Throughput and it is a PHY defined by the 802.11af amendment. It uses the TV white space (TVWS) spectrum in the VHF and UHF bands between 54 and 790 MHz, which are not in use by broadcast video signals at the time. It can provide long-range and low-power connectivity for WLAN devices.